title
C Programming Language - Intro to Computer Science - Harvard's CS50 (2018)

description
Learn the the basics of the C programming language. This course teaches the foundations of computer science. This video is lecture 1 of Harvard University's CS50 2018 course (part 2 since the lectures start at 0). 🔗Notes: https://cs50.harvard.edu/x/2020/notes/1/ 🔗Problem Set: https://cs50.harvard.edu/x/2020/psets/1/ 🔗Source Code: https://cdn.cs50.net/2019/fall/lectures/1/src1.zip ⭐️Contents⭐️ ⌨️ (00:00:00) Introduction ⌨️ (00:00:50) Week 0 Recap ⌨️ (00:08:01) PBJ ⌨️ (00:15:59) C ⌨️ (00:20:56) Variables ⌨️ (00:21:46) Incrementing ⌨️ (00:23:36) Conditionals ⌨️ (00:32:31) While Loops ⌨️ (00:35:52) For Loops ⌨️ (00:40:47) User Input ⌨️ (00:48:14) CS50 Sandbox ⌨️ (00:49:48) hello.c ⌨️ (00:51:18) Compilation ⌨️ (00:57:31) Command-Line Arguments ⌨️ (00:58:50) make ⌨️ (00:58:30) Debugging ⌨️ (01:11:44) get_string and printf ⌨️ (01:18:23) int.c ⌨️ (01:21:58) float.c ⌨️ (01:24:29) ints.c ⌨️ (01:28:39) floats.c ⌨️ (01:37:54) parity.c ⌨️ (01:39:13) conditions.c ⌨️ (01:40:17) answer.c ⌨️ (01:42:15) cough0.c ⌨️ (01:42:57) cough1.c ⌨️ (01:43:57) cough2.c ⌨️ (01:49:53) cough3.c ⌨️ (01:52:04) positive.c ⌨️ (01:58:05) Integer Overflow ⌨️ (02:03:04) overflow.c ⌨️ (02:09:50) Integer Underflow Check out our full CS50 playlist: https://www.youtube.com/playlist?list=PLWKjhJtqVAbmGw5fN5BQlwuug-8bDmabi 🔗Notes: https://cs50.harvard.edu/college/weeks/1/notes/ 🔗Problem Set: https://cs50.harvard.edu/college/psets/1/ 🔗Source Code: https://cdn.cs50.net/2018/fall/lectures/1/src1/ Lecture taught by David J. Malan. Thanks to Harvard's CS50 for giving us permission to post this lecture. Checkout their YouTube channel for more great lectures: https://www.youtube.com/cs50 -- Learn to code for free and get a developer job: https://www.freecodecamp.org Read hundreds of articles on programming: https://medium.freecodecamp.org

detail
{'title': "C Programming Language - Intro to Computer Science - Harvard's CS50 (2018)", 'heatmap': [{'end': 6078.671, 'start': 5995.26, 'weight': 1}], 'summary': 'Covers various chapters including binary representation, transition to c programming, coding logic, basics of looping, user input and functions, cs50 sandbox, command line environment, c programming fundamentals, precision, functions and loops, and integer overflow in computing.', 'chapters': [{'end': 785.557, 'segs': [{'end': 235.589, 'src': 'embed', 'start': 181.397, 'weight': 0, 'content': [{'end': 183.858, 'text': "But we don't need to think about the world at that level.", 'start': 181.397, 'duration': 2.461}, {'end': 185.119, 'text': 'We can abstract on top of that.', 'start': 183.878, 'duration': 1.241}, {'end': 187.48, 'text': 'All of us are so much more familiar with decimal, of course.', 'start': 185.159, 'duration': 2.321}, {'end': 194.003, 'text': 'And indeed recall that this was just 72, 73, and 33, which, if anyone recalls when you use ASCII,', 'start': 187.74, 'duration': 6.263}, {'end': 197.345, 'text': 'which is this global standard for mapping numbers to letters, we got what message?', 'start': 194.003, 'duration': 3.342}, {'end': 201.941, 'text': 'Yeah, it was just hi capital H, capital I exclamation point.', 'start': 198.339, 'duration': 3.602}, {'end': 206.283, 'text': "And so that's an abstraction on top of those otherwise binary numbers.", 'start': 201.981, 'duration': 4.302}, {'end': 209.245, 'text': "But we don't have to model just text using numbers.", 'start': 206.344, 'duration': 2.901}, {'end': 212.467, 'text': 'At the end of the day, our only resource is still that electricity.', 'start': 209.505, 'duration': 2.962}, {'end': 215.028, 'text': 'And the only way we think about it digitally is still zeros and ones.', 'start': 212.527, 'duration': 2.501}, {'end': 223.836, 'text': 'But if we take these same values 72,, 73, 33, and treat them in the context of like Photoshop or like a photo program or a graphics program,', 'start': 215.269, 'duration': 8.567}, {'end': 229.062, 'text': 'we can instead interpret them as like some amount of red, some amount of green, some amount of blue, which gave us last time.', 'start': 223.836, 'duration': 5.226}, {'end': 230.444, 'text': 'recall this yellowish color.', 'start': 229.062, 'duration': 1.382}, {'end': 234.008, 'text': 'So now we had another abstraction on top of binary colors.', 'start': 230.804, 'duration': 3.204}, {'end': 235.589, 'text': 'And this is just one pixel.', 'start': 234.388, 'duration': 1.201}], 'summary': 'Understanding binary and abstractions in computer science, demonstrating with ascii and color values.', 'duration': 54.192, 'max_score': 181.397, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M181397.jpg'}, {'end': 314.824, 'src': 'embed', 'start': 284.537, 'weight': 3, 'content': [{'end': 286.178, 'text': "And that's the value of abstraction.", 'start': 284.537, 'duration': 1.641}, {'end': 290.602, 'text': 'But inside of this black box were so-called algorithms, the sort of secret sauce.', 'start': 286.758, 'duration': 3.844}, {'end': 292.905, 'text': 'This is where the problems are actually solved.', 'start': 290.662, 'duration': 2.243}, {'end': 299.131, 'text': 'And we not only talked about what these algorithms are, but for instance, how efficient they were.', 'start': 293.265, 'duration': 5.866}, {'end': 305.198, 'text': 'So recall that this red line represented a very simple algorithm, just turning the phone book page by page, one at a time.', 'start': 299.231, 'duration': 5.967}, {'end': 312.342, 'text': "And the reason that it's a straight line is because there's like a 1 to 1 correspondence between how many pages there are in the book and how many page turns there are.", 'start': 305.478, 'duration': 6.864}, {'end': 314.824, 'text': 'One more page, one more turn, and so forth.', 'start': 312.502, 'duration': 2.322}], 'summary': "Algorithms' efficiency illustrated with 1:1 correspondence, representing value of abstraction.", 'duration': 30.287, 'max_score': 284.537, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M284537.jpg'}, {'end': 402.439, 'src': 'embed', 'start': 375.204, 'weight': 4, 'content': [{'end': 380.786, 'text': 'And recall that along the way, we introduced a whole bunch of concepts, many of which you probably experimented with Scratch,', 'start': 375.204, 'duration': 5.582}, {'end': 386.168, 'text': 'like loops and conditions, Boolean expressions, variables and so forth.', 'start': 380.786, 'duration': 5.382}, {'end': 390.49, 'text': 'And those were building blocks that kind of came out of this kind of demonstration here.', 'start': 386.408, 'duration': 4.082}, {'end': 395.754, 'text': 'But honestly, even in this demonstration, in this pseudocode, there were a whole bunch of assumptions.', 'start': 391.05, 'duration': 4.704}, {'end': 402.439, 'text': "If you read these instructions one at a time and you're holding the phone book yourself, odds are you can execute the pseudocode, this algorithm.", 'start': 396.254, 'duration': 6.185}], 'summary': 'Introduced various programming concepts including loops, conditions, boolean expressions, and variables in scratch.', 'duration': 27.235, 'max_score': 375.204, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M375204.jpg'}, {'end': 590.397, 'src': 'embed', 'start': 557.959, 'weight': 5, 'content': [{'end': 559.439, 'text': "And Brian's going to scribe as we go.", 'start': 557.959, 'duration': 1.48}, {'end': 565.341, 'text': 'And all we want to do this morning is just make a peanut butter and jelly sandwich, one instruction at a time.', 'start': 559.479, 'duration': 5.862}, {'end': 566.961, 'text': 'And each of us will just execute what we hear.', 'start': 565.381, 'duration': 1.58}, {'end': 568.021, 'text': "How's that sound? Good.", 'start': 567.541, 'duration': 0.48}, {'end': 568.621, 'text': 'DAVID J.', 'start': 568.041, 'duration': 0.58}, {'end': 570.782, 'text': 'All right, if someone could volunteer with the first instruction.', 'start': 568.621, 'duration': 2.161}, {'end': 571.822, 'text': 'And Brian will type it down.', 'start': 570.962, 'duration': 0.86}, {'end': 577.854, 'text': 'Open bread, we heard.', 'start': 576.954, 'duration': 0.9}, {'end': 579.174, 'text': 'Open bread is the first instruction.', 'start': 577.934, 'duration': 1.24}, {'end': 580.995, 'text': "So if you'd each like to execute open bread.", 'start': 579.194, 'duration': 1.801}, {'end': 590.397, 'text': "Don't look at me.", 'start': 587.556, 'duration': 2.841}], 'summary': 'Participants make a peanut butter and jelly sandwich one instruction at a time using verbal communication.', 'duration': 32.438, 'max_score': 557.959, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M557959.jpg'}], 'start': 0.571, 'title': 'Binary, abstractions, algorithms, and pseudocode', 'summary': 'Covers the introduction to binary representation in programming and progresses to the use of abstractions in algorithms, including pseudocode for expressing precise instructions. it also demonstrates the challenges of abstraction in programming through a peanut butter and jelly sandwich activity.', 'chapters': [{'end': 265.892, 'start': 0.571, 'title': 'Cs50: week 1 - introduction to binary and abstractions', 'summary': 'Introduces the concept of binary and abstractions in programming, highlighting the progression from binary representation to text, color, and images, ultimately leading to animations and videos.', 'duration': 265.321, 'highlights': ['The chapter introduces the concept of binary and its significance in programming, highlighting the progression from binary representation to text, color, and images.', "The significance of binary in representing states and its abstraction into text using ASCII is explained, showcasing a practical example of binary numbers representing the message 'hi!'", 'The concept of color representation in graphics using binary values is introduced, showcasing the abstraction of binary into pixel color representation.']}, {'end': 785.557, 'start': 265.892, 'title': 'Algorithms and abstraction', 'summary': 'Discusses the value of abstraction in algorithms, the use of pseudocode for expressing precise instructions, and the challenges of abstraction in programming, demonstrated through a peanut butter and jelly sandwich activity.', 'duration': 519.665, 'highlights': ['The value of abstraction in algorithms is highlighted, emphasizing the importance of representing inputs and outputs and the efficiency of algorithms, demonstrated through different approaches to finding a name in a phone book.', 'The use of pseudocode as a more precise way to express algorithms is demonstrated, introducing concepts like loops, conditions, and variables as building blocks for expressing instructions.', "The challenges of abstraction in programming are illustrated through a peanut butter and jelly sandwich activity, showcasing the need for precise instructions and the potential ambiguity in expressing actions like 'open to the middle of the phone book' and 'call Mike'."]}], 'duration': 784.986, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M571.jpg', 'highlights': ['The chapter introduces the concept of binary and its significance in programming, showcasing progression to text, color, and images.', "The significance of binary in representing states and its abstraction into text using ASCII is explained, demonstrating binary numbers representing the message 'hi!'", 'The concept of color representation in graphics using binary values is introduced, showcasing the abstraction of binary into pixel color representation.', 'The value of abstraction in algorithms is highlighted, emphasizing the importance of representing inputs and outputs and the efficiency of algorithms.', 'The use of pseudocode as a more precise way to express algorithms is demonstrated, introducing concepts like loops, conditions, and variables.', 'The challenges of abstraction in programming are illustrated through a peanut butter and jelly sandwich activity, showcasing the need for precise instructions.']}, {'end': 1626.864, 'segs': [{'end': 911.38, 'src': 'embed', 'start': 877.447, 'weight': 3, 'content': [{'end': 879.487, 'text': 'And I think the instructions were kind of helping with that here.', 'start': 877.447, 'duration': 2.04}, {'end': 887.269, 'text': "But when it comes time to program with Scratch and certainly with C starting this week, you can't really make as many of those assumptions anymore.", 'start': 880.108, 'duration': 7.161}, {'end': 891.83, 'text': "Because if you don't handle these sort of corner cases and if you don't think about what that instruction means,", 'start': 887.369, 'duration': 4.461}, {'end': 896.513, 'text': "You're going to get the proverbial spinning beach ball or the hourglass that you're familiar with on your Mac or PC.", 'start': 892.47, 'duration': 4.043}, {'end': 897.633, 'text': "The program's going to crash.", 'start': 896.533, 'duration': 1.1}, {'end': 902.956, 'text': "Something's going to go wrong just because you missed some specificity or precision.", 'start': 897.954, 'duration': 5.002}, {'end': 911.38, 'text': "Now, we're so over time, we're going to find that much like in Scratch, we were able to make our own building blocks.", 'start': 903.517, 'duration': 7.863}], 'summary': 'In programming, missing precision can lead to crashes and errors; specificity is crucial.', 'duration': 33.933, 'max_score': 877.447, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M877447.jpg'}, {'end': 1053.503, 'src': 'embed', 'start': 996.994, 'weight': 2, 'content': [{'end': 1003.582, 'text': 'And frankly, even after doing Scratch, anyone, even with no prior background, can probably hazard a guess as to what this program,', 'start': 996.994, 'duration': 6.588}, {'end': 1005.985, 'text': 'written in this other language called C, does when you run it.', 'start': 1003.582, 'duration': 2.403}, {'end': 1009.096, 'text': 'It just prints hello world.', 'start': 1007.574, 'duration': 1.522}, {'end': 1012.5, 'text': "Now granted, there's a decent amount of overhead syntactically.", 'start': 1009.196, 'duration': 3.304}, {'end': 1016.124, 'text': "There's a bunch of stuff you have to type to make this program do what you want it to do.", 'start': 1012.54, 'duration': 3.584}, {'end': 1018.808, 'text': "But at the end of the day, that's all it's going to do.", 'start': 1016.385, 'duration': 2.423}, {'end': 1024.054, 'text': "And this is among the simplest of programs we're going to add to our puzzle pieces, so to speak, today in C.", 'start': 1019.068, 'duration': 4.986}, {'end': 1027.637, 'text': 'some of those same concepts that we saw last time as well.', 'start': 1024.795, 'duration': 2.842}, {'end': 1029.5, 'text': "So let's do this first, though.", 'start': 1027.917, 'duration': 1.583}, {'end': 1036.067, 'text': 'Let me take a moment to sort of compare Scratch to C, because the most important takeaway for today is going to be that,', 'start': 1029.74, 'duration': 6.327}, {'end': 1043.394, 'text': "even if the syntax doesn't look so obvious, and, frankly, even if your first minutes or hours with writing your own code in C is frustrating because,", 'start': 1036.067, 'duration': 7.327}, {'end': 1047.358, 'text': 'ah, damn it, like you left off a semicolon, or oh, I had a parenthesis in the wrong place.', 'start': 1043.394, 'duration': 3.964}, {'end': 1051.922, 'text': "There's a lot of these stupid syntactic hangups that make you feel quite often that you really aren't getting it.", 'start': 1047.377, 'duration': 4.545}, {'end': 1053.503, 'text': "But that's not the important stuff.", 'start': 1052.222, 'duration': 1.281}], 'summary': 'In c, even simple programs involve significant syntactic overhead, but the most important takeaway is understanding the concepts despite initial frustration.', 'duration': 56.509, 'max_score': 996.994, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M996994.jpg'}, {'end': 1301.97, 'src': 'embed', 'start': 1274.653, 'weight': 0, 'content': [{'end': 1280.836, 'text': "We're going to say literally the name of the variable we want, for instance counter, but we could call it anything we want equals 0,", 'start': 1274.653, 'duration': 6.183}, {'end': 1283.018, 'text': "if we're setting it initially, equal to 0..", 'start': 1280.836, 'duration': 2.182}, {'end': 1284.939, 'text': 'But C is a little more pedantic.', 'start': 1283.018, 'duration': 1.921}, {'end': 1292.183, 'text': "You've also got to tell the computer, this type of variable I want is specifically for an integer, otherwise abbreviated int.", 'start': 1284.999, 'duration': 7.184}, {'end': 1296.226, 'text': "So you have to tell the computer in events what type of data you're going to store in it and take a guess.", 'start': 1292.503, 'duration': 3.723}, {'end': 1301.97, 'text': "You've got to finish the thought and see what more do we need to add to the? Yeah, just a semicolon.", 'start': 1296.666, 'duration': 5.304}], 'summary': 'In c, variables need to be explicitly declared with their data type, such as int, before use.', 'duration': 27.317, 'max_score': 1274.653, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M1274653.jpg'}, {'end': 1446.507, 'src': 'embed', 'start': 1420.865, 'weight': 1, 'content': [{'end': 1425.569, 'text': 'Yeah, we called this a condition, and it had a Boolean expression that we were asking a question of.', 'start': 1420.865, 'duration': 4.704}, {'end': 1431.235, 'text': "In this case, we're apparently asking in Scratch, is x less than y? And if so, say it on the screen.", 'start': 1425.85, 'duration': 5.385}, {'end': 1436.499, 'text': 'So how might we translate this to C? Well, it turns out we can quite simply translate this one pretty literally.', 'start': 1431.295, 'duration': 5.204}, {'end': 1441.484, 'text': "We've seen almost all of the building blocks thus far, but we do have to introduce a little something new here.", 'start': 1436.76, 'duration': 4.724}, {'end': 1443.426, 'text': 'Notice that the printf line.', 'start': 1441.924, 'duration': 1.502}, {'end': 1446.507, 'text': 'is almost identical to what I used earlier for just hello world.', 'start': 1443.966, 'duration': 2.541}], 'summary': 'Translating a condition from scratch to c, involving x and y comparison.', 'duration': 25.642, 'max_score': 1420.865, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M1420865.jpg'}], 'start': 785.557, 'title': 'Transition to c programming', 'summary': 'Introduces the transition from graphical programming language scratch to the text-based language c, emphasizing the need for precision when programming, discussing variables, declarations, usage, and conditions, and highlighting the importance of syntax and style in programming.', 'chapters': [{'end': 1256.945, 'start': 785.557, 'title': 'Introduction to text-based programming', 'summary': 'Introduces the transition from graphical programming language scratch to the text-based language c, emphasizing the need for precision when programming and highlighting the differences and similarities between the two languages.', 'duration': 471.388, 'highlights': ['The transition from Scratch to C programming language is introduced, emphasizing the need for precision to avoid program crashes.', 'Comparison between Scratch and C programming languages is made, emphasizing the importance of principles over syntax in programming.', 'Explanation of the differences in syntax and requirements between Scratch and C programming languages is provided.']}, {'end': 1626.864, 'start': 1257.565, 'title': 'Variables and conditions in c', 'summary': 'Discusses the concept of variables in c, including the definition, declaration, and usage of variables, as well as the translation of conditions from scratch to c, highlighting the importance of syntax and style in programming.', 'duration': 369.299, 'highlights': ['Variables in C', 'Incrementing Variables in C', 'Translation of Conditions from Scratch to C', 'Importance of Syntax and Style in Programming']}], 'duration': 841.307, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M785557.jpg', 'highlights': ['Variables in C', 'Translation of Conditions from Scratch to C', 'Importance of Syntax and Style in Programming', 'The transition from Scratch to C programming language is introduced, emphasizing the need for precision to avoid program crashes.', 'Comparison between Scratch and C programming languages is made, emphasizing the importance of principles over syntax in programming.', 'Explanation of the differences in syntax and requirements between Scratch and C programming languages is provided.', 'Incrementing Variables in C']}, {'end': 2098.372, 'segs': [{'end': 1676.968, 'src': 'embed', 'start': 1649.372, 'weight': 3, 'content': [{'end': 1654.639, 'text': "And we'll see examples of that before long, where you can actually say give me a variable called counter,", 'start': 1649.372, 'duration': 5.267}, {'end': 1656.521, 'text': "but don't actually set it equal to some value.", 'start': 1654.639, 'duration': 1.882}, {'end': 1657.903, 'text': 'Come back to that in a bit.', 'start': 1657.042, 'duration': 0.861}, {'end': 1664.403, 'text': "All right, so what if we want to add this logic? Frankly, in Scratch, it's starting to look a little overwhelming.", 'start': 1658.84, 'duration': 5.563}, {'end': 1666.483, 'text': 'But this is just a three-way fork in the road.', 'start': 1664.643, 'duration': 1.84}, {'end': 1668.424, 'text': 'If x is less than y, say so.', 'start': 1666.604, 'duration': 1.82}, {'end': 1671.906, 'text': 'Else if x is greater than y, say so.', 'start': 1669.105, 'duration': 2.801}, {'end': 1676.968, 'text': "Else if x equals y, then go ahead and say they're equal.", 'start': 1672.526, 'duration': 4.442}], 'summary': 'Exploring conditional logic with three-way fork in the road', 'duration': 27.596, 'max_score': 1649.372, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M1649372.jpg'}, {'end': 1765.532, 'src': 'embed', 'start': 1738.359, 'weight': 0, 'content': [{'end': 1743.76, 'text': "But if we've already used the equal sign for assignment, we need another pattern of symbols to represent equality.", 'start': 1738.359, 'duration': 5.401}, {'end': 1747.381, 'text': 'And as it turns out, humans just chose two equal signs instead.', 'start': 1744.04, 'duration': 3.341}, {'end': 1749.062, 'text': 'Slightly different from Scratch.', 'start': 1747.981, 'duration': 1.081}, {'end': 1752.984, 'text': "The reason Scratch does it this way is because you don't really want to have to get into those weeds.", 'start': 1749.302, 'duration': 3.682}, {'end': 1757.427, 'text': "Certainly, when the target audience is eight-year-olds just learning to program in the first place, it's not important.", 'start': 1753.024, 'duration': 4.403}, {'end': 1758.968, 'text': 'Nor is it really important for us.', 'start': 1757.727, 'duration': 1.241}, {'end': 1762.81, 'text': "But for us, there's going to be a logical difference.", 'start': 1759.028, 'duration': 3.782}, {'end': 1765.532, 'text': 'Because if we use the wrong one, the behavior is going to be wrong.', 'start': 1763.291, 'duration': 2.241}], 'summary': 'Using two equal signs instead of one for equality, different from scratch, important for logical correctness.', 'duration': 27.173, 'max_score': 1738.359, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M1738359.jpg'}, {'end': 1845.303, 'src': 'embed', 'start': 1816.073, 'weight': 2, 'content': [{'end': 1819.896, 'text': "But logically, this is not necessary, right? Let's make the program a little better designed.", 'start': 1816.073, 'duration': 3.823}, {'end': 1828.123, 'text': 'How many possible cases are there when comparing two integers, x and y for greater than less than or equality??', 'start': 1820.417, 'duration': 7.706}, {'end': 1830.245, 'text': "Oh, I just answered the question, didn't I??", 'start': 1829.084, 'duration': 1.161}, {'end': 1832.858, 'text': 'Is there a three??', 'start': 1831.638, 'duration': 1.22}, {'end': 1833.619, 'text': 'Excellent.', 'start': 1833.259, 'duration': 0.36}, {'end': 1834.919, 'text': "There's three scenarios there.", 'start': 1833.639, 'duration': 1.28}, {'end': 1838.14, 'text': 'x is either less than or greater than or equal to.', 'start': 1835.039, 'duration': 3.101}, {'end': 1840.321, 'text': "And I'm hard pressed to think of a fourth.", 'start': 1838.18, 'duration': 2.141}, {'end': 1845.303, 'text': 'So do I need this amount of specificity?', 'start': 1841.402, 'duration': 3.901}], 'summary': 'Designing a program to compare two integers for 3 scenarios: less than, greater than, or equal to.', 'duration': 29.23, 'max_score': 1816.073, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M1816073.jpg'}, {'end': 1974.532, 'src': 'embed', 'start': 1934.919, 'weight': 1, 'content': [{'end': 1937.561, 'text': "If it's more clear from the code what's going on, leave it that way.", 'start': 1934.919, 'duration': 2.642}, {'end': 1940.944, 'text': "But these are the kinds of design decisions that we'll now make.", 'start': 1938.122, 'duration': 2.822}, {'end': 1946.669, 'text': 'And, arguably, this version of the Scratch program and this version of the C code is just a little better design,', 'start': 1941.084, 'duration': 5.585}, {'end': 1951.093, 'text': 'because why write more code than you need to to express the exact same idea?', 'start': 1946.669, 'duration': 4.424}, {'end': 1953.431, 'text': 'All right, so what about this?', 'start': 1952.23, 'duration': 1.201}, {'end': 1955.313, 'text': 'This was a loop in Scratch.', 'start': 1953.791, 'duration': 1.522}, {'end': 1958.536, 'text': 'This was an infinite loop because it was just forever saying hello world.', 'start': 1955.353, 'duration': 3.183}, {'end': 1961.819, 'text': 'Now in C, this gets a little less directly translated.', 'start': 1958.796, 'duration': 3.023}, {'end': 1963.84, 'text': 'Turns out C uses the keyword while.', 'start': 1961.879, 'duration': 1.961}, {'end': 1967.464, 'text': 'So there is no forever keyword in C, but there is the word while.', 'start': 1964.101, 'duration': 3.363}, {'end': 1974.532, 'text': "And of course, I'm going to use my curly braces or curly braces, curly brackets to kind of encompass the following lines of code.", 'start': 1967.964, 'duration': 6.568}], 'summary': 'Comparing design decisions between scratch and c code, emphasizing efficiency and translation challenges.', 'duration': 39.613, 'max_score': 1934.919, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M1934919.jpg'}], 'start': 1626.864, 'title': 'Coding logic and design differences', 'summary': 'Discusses coding logic and variable declaration, translating logic from scratch to c, differences in handling logical expressions and symbols between scratch and c, and design disparities emphasizing concise code and loop structures.', 'chapters': [{'end': 1693.958, 'start': 1626.864, 'title': 'Coding logic and variable declaration', 'summary': 'Discusses coding logic and variable declaration, including the idea of not setting a variable equal to something right away and the translation of logic from scratch to c language.', 'duration': 67.094, 'highlights': ['The idea of not setting a variable equal to something right away is explained, with examples to follow shortly.', 'The translation of logic from Scratch to C language, including the use of if-else statements based on comparisons of variables, is discussed.', 'The concept of establishing the countervariable and its relevance is addressed in response to a question from the audience.']}, {'end': 1934.759, 'start': 1693.958, 'title': 'Scratch and c: symbols and logical expressions', 'summary': 'Discusses the differences between scratch and c in handling logical expressions and symbols, highlighting the use of double equal signs for equality, the need for specificity in logical comparisons, and the trade-offs between code optimization and readability.', 'duration': 240.801, 'highlights': ['The use of double equal signs in C for equality is a deliberate difference from Scratch, necessitated by the need for a separate symbol due to the assignment operation using a single equal sign.', 'The discussion on the need for specificity in logical comparisons, highlighting the three possible scenarios when comparing two integers for greater than, less than, or equality.', 'The trade-off between code optimization and readability, illustrated through the example of unnecessary questions asked in logical comparisons and the consideration of factors like computer speed and code readability.']}, {'end': 2098.372, 'start': 1934.919, 'title': 'Design decisions in scratch vs. c', 'summary': 'Explains the design differences between scratch and c, emphasizing the need for concise code and the use of while loops in c to achieve infinite loops, along with the concept of true and false keywords for loop conditions.', 'duration': 163.453, 'highlights': ['C uses while loops to achieve infinite loops, requiring a condition to be checked each time the loop executes.', 'The use of true and false keywords in C to create an infinite loop by consistently evaluating a condition to true.', 'Emphasizing the need for concise code and avoiding unnecessary repetition in design decisions for Scratch and C.']}], 'duration': 471.508, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M1626864.jpg', 'highlights': ['The use of double equal signs in C for equality is a deliberate difference from Scratch, necessitated by the need for a separate symbol due to the assignment operation using a single equal sign.', 'C uses while loops to achieve infinite loops, requiring a condition to be checked each time the loop executes.', 'The discussion on the need for specificity in logical comparisons, highlighting the three possible scenarios when comparing two integers for greater than, less than, or equality.', 'The idea of not setting a variable equal to something right away is explained, with examples to follow shortly.', 'The translation of logic from Scratch to C language, including the use of if-else statements based on comparisons of variables, is discussed.']}, {'end': 2447.628, 'segs': [{'end': 2127.464, 'src': 'embed', 'start': 2098.832, 'weight': 2, 'content': [{'end': 2104.915, 'text': "All of the examples I'll show here today and you'll see in the coming weeks are sort of the better way to do things because they're more readable.", 'start': 2098.832, 'duration': 6.083}, {'end': 2109.697, 'text': "But again, as you get more comfortable with code or if you're coming in with some prior experience, you might already have your own opinions.", 'start': 2105.195, 'duration': 4.502}, {'end': 2114.158, 'text': 'And frankly, this is just a religious debate among programmers which is the right way to write your code.', 'start': 2109.997, 'duration': 4.161}, {'end': 2114.999, 'text': "And that's fine.", 'start': 2114.438, 'duration': 0.561}, {'end': 2118.16, 'text': "Once you get comfy, so long as you're consistent is the most important thing.", 'start': 2115.059, 'duration': 3.101}, {'end': 2120.301, 'text': "You don't need to adhere to one person's or the other.", 'start': 2118.2, 'duration': 2.101}, {'end': 2122.402, 'text': 'So how does this code work logically??', 'start': 2120.801, 'duration': 1.601}, {'end': 2127.464, 'text': "Well, the first thing the computer, your Mac or PC, or your phone or whatever is going to do, it's going to ask the question.", 'start': 2122.602, 'duration': 4.862}], 'summary': 'Debate among programmers on the right way to write code, prioritize consistency over adherence to a specific style.', 'duration': 28.632, 'max_score': 2098.832, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M2098832.jpg'}, {'end': 2248.58, 'src': 'embed', 'start': 2224.141, 'weight': 0, 'content': [{'end': 2230.104, 'text': "to how many times we've already executed this code, and then constantly make sure that one does not exceed the other.", 'start': 2224.141, 'duration': 5.963}, {'end': 2232.286, 'text': 'So we stop once we hit 50.', 'start': 2230.164, 'duration': 2.122}, {'end': 2240.334, 'text': "So what's the sort of fundamental construct that we use to keep track of anything in a program? counter, which was an example of a variable.", 'start': 2232.286, 'duration': 8.048}, {'end': 2241.936, 'text': 'So we just need to use a variable.', 'start': 2240.434, 'duration': 1.502}, {'end': 2244.898, 'text': "Now, it's actually going to be inside of the parentheses this time.", 'start': 2242.176, 'duration': 2.722}, {'end': 2246.979, 'text': "So it's not on its own as it was just a bit ago.", 'start': 2244.938, 'duration': 2.041}, {'end': 2248.58, 'text': 'But the syntax is the same.', 'start': 2247.339, 'duration': 1.241}], 'summary': 'Code executed 50 times using a counter variable.', 'duration': 24.439, 'max_score': 2224.141, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M2224141.jpg'}, {'end': 2447.628, 'src': 'embed', 'start': 2400.161, 'weight': 3, 'content': [{'end': 2403.483, 'text': 'Now go ahead and execute the code, and again, and again, and again.', 'start': 2400.161, 'duration': 3.322}, {'end': 2408.326, 'text': "And at some point, we're going to get up to i equals 49.", 'start': 2404.063, 'duration': 4.263}, {'end': 2410.888, 'text': 'And is 49 less than 50? Obviously.', 'start': 2408.326, 'duration': 2.562}, {'end': 2412.348, 'text': 'So we print out hello world.', 'start': 2410.948, 'duration': 1.4}, {'end': 2414.73, 'text': 'And then i++ kicks in.', 'start': 2413.249, 'duration': 1.481}, {'end': 2418.792, 'text': "And then it's, is 50 less than 50? No.", 'start': 2415.27, 'duration': 3.522}, {'end': 2421.213, 'text': 'So wait, that feels like a logical error, though, no?', 'start': 2418.932, 'duration': 2.281}, {'end': 2425.205, 'text': 'Should I be checking if i is less than or equal to 50??', 'start': 2421.233, 'duration': 3.972}, {'end': 2428.889, 'text': 'Yeah, because if I started from 0, I already spent that one additional cycle.', 'start': 2425.205, 'duration': 3.684}, {'end': 2434.875, 'text': 'So I can count from 0 through 49, which seems to work, or from 1 through 50.', 'start': 2428.929, 'duration': 5.946}, {'end': 2442.724, 'text': 'But the convention in programming honestly, is typically to start counting at some value and then count up to, but not through some value,', 'start': 2434.875, 'duration': 7.849}, {'end': 2443.344, 'text': 'just because.', 'start': 2442.724, 'duration': 0.62}, {'end': 2447.628, 'text': 'But logically, you can implement this in half a dozen different ways, most likely.', 'start': 2444.105, 'duration': 3.523}], 'summary': 'Demonstrating a loop with i counting from 0 to 49', 'duration': 47.467, 'max_score': 2400.161, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M2400161.jpg'}], 'start': 2098.832, 'title': 'Basics of looping in c programming', 'summary': "Covers fundamental concepts of looping in c programming, emphasizing variables, naming conventions, rationale for starting counting from 0, use of 'for' loop, and the importance of consistent coding practices. it also discusses loop iteration, conditional statements, and logic behind setting the range of iteration from 0 to 49 or 1 to 50.", 'chapters': [{'end': 2323.026, 'start': 2098.832, 'title': 'Looping in c programming', 'summary': "Discusses the fundamental concepts of looping in c programming, emphasizing the use of variables, conventions for naming variables, and the rationale for starting counting from 0 rather than 1 in computers. it also highlights the use of 'for' loop and the importance of being consistent in coding practices.", 'duration': 224.194, 'highlights': ['The chapter discusses the fundamental concepts of looping in C programming, emphasizing the use of variables, conventions for naming variables, and the rationale for starting counting from 0 rather than 1 in computers.', "It also highlights the use of 'for' loop and the importance of being consistent in coding practices."]}, {'end': 2447.628, 'start': 2323.026, 'title': 'Loop iteration and conditional statements', 'summary': "Discusses the use of loops to iterate through code, incrementing a variable and checking a conditional statement to execute code, resulting in the output of 'hello world' and the logic behind setting the range of iteration from 0 to 49 or 1 to 50.", 'duration': 124.602, 'highlights': ['The chapter discusses the use of loops to iterate through code, incrementing a variable and checking a conditional statement to execute code.', "The output of 'hello world' is printed when the condition 'i is less than 50' is true and 'i' is incremented to 49.", 'The logic behind setting the range of iteration from 0 to 49 or 1 to 50 is discussed, highlighting the convention of starting at some value and counting up to, but not through, some value.']}], 'duration': 348.796, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M2098832.jpg', 'highlights': ['The chapter discusses the fundamental concepts of looping in C programming, emphasizing the use of variables, conventions for naming variables, and the rationale for starting counting from 0 rather than 1 in computers.', 'The chapter discusses the use of loops to iterate through code, incrementing a variable and checking a conditional statement to execute code.', "It also highlights the use of 'for' loop and the importance of being consistent in coding practices.", 'The logic behind setting the range of iteration from 0 to 49 or 1 to 50 is discussed, highlighting the convention of starting at some value and counting up to, but not through, some value.', "The output of 'hello world' is printed when the condition 'i is less than 50' is true and 'i' is incremented to 49."]}, {'end': 2876.056, 'segs': [{'end': 2475.914, 'src': 'embed', 'start': 2447.648, 'weight': 0, 'content': [{'end': 2452.733, 'text': "All right, let's look at one final example that allowed us to actually get user input in Scratch.", 'start': 2447.648, 'duration': 5.085}, {'end': 2457.257, 'text': 'Recall that we used this block to actually get the name of someone in lecture.', 'start': 2452.793, 'duration': 4.464}, {'end': 2461.661, 'text': 'And we also, in the animation with the gingerbread house, used it to get yes or no.', 'start': 2457.317, 'duration': 4.344}, {'end': 2463.443, 'text': 'Do you want the cupcake or the apple or the like?', 'start': 2461.681, 'duration': 1.762}, {'end': 2469.909, 'text': "So this is an example of a function in Scratch that actually takes input like the sentence what's your name?", 'start': 2463.763, 'duration': 6.146}, {'end': 2475.914, 'text': 'but it also returns a value which in this case was just hard coded in Scratch by MIT to be called answer.', 'start': 2469.909, 'duration': 6.005}], 'summary': 'Scratch allows user input with example of getting name and yes/no responses.', 'duration': 28.266, 'max_score': 2447.648, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M2447648.jpg'}, {'end': 2518.025, 'src': 'embed', 'start': 2483.381, 'weight': 1, 'content': [{'end': 2490.806, 'text': 'In C, It turns out that you can express this line of code a little more verbosely than before by using a new function called get string.', 'start': 2483.381, 'duration': 7.425}, {'end': 2493.548, 'text': 'So get underscore string is the name of the function.', 'start': 2491.206, 'duration': 2.342}, {'end': 2495.689, 'text': 'The underscore is convention in C.', 'start': 2493.588, 'duration': 2.101}, {'end': 2498.531, 'text': "If you ever want to have a space, you can't have spaces in the names of functions.", 'start': 2495.689, 'duration': 2.842}, {'end': 2503.534, 'text': 'So people just started using underscores, like you might in your own social media usernames and the like.', 'start': 2498.591, 'duration': 4.943}, {'end': 2504.935, 'text': "It's a convention there as well.", 'start': 2503.574, 'duration': 1.361}, {'end': 2508.217, 'text': "Here's the sentence I want to display.", 'start': 2505.515, 'duration': 2.702}, {'end': 2510.899, 'text': "And I'm going to start calling this more formally a string.", 'start': 2508.758, 'duration': 2.141}, {'end': 2514.422, 'text': 'A string in a programming language is just a sequence of characters.', 'start': 2511.28, 'duration': 3.142}, {'end': 2517.064, 'text': "Like it's a word, it's a phrase, it's a character, it's a paragraph.", 'start': 2514.462, 'duration': 2.602}, {'end': 2518.025, 'text': 'This is a string.', 'start': 2517.345, 'duration': 0.68}], 'summary': 'In c, get_string is a convention for expressing code more verbosely, representing a sequence of characters.', 'duration': 34.644, 'max_score': 2483.381, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M2483381.jpg'}, {'end': 2639.822, 'src': 'embed', 'start': 2615.467, 'weight': 2, 'content': [{'end': 2624.052, 'text': "If you're not passing in a hard-coded string or sentence, you have to pass to printf what's called a format code or a format string.", 'start': 2615.467, 'duration': 8.585}, {'end': 2628.835, 'text': 'This first input to printf, now printf apparently seems to take two things.', 'start': 2624.533, 'duration': 4.302}, {'end': 2631.036, 'text': 'The first is this one before the comma.', 'start': 2629.255, 'duration': 1.781}, {'end': 2632.998, 'text': 'The second is the thing after the comma.', 'start': 2631.337, 'duration': 1.661}, {'end': 2635.699, 'text': "And we've not seen this before yet in C.", 'start': 2633.018, 'duration': 2.681}, {'end': 2639.822, 'text': 'So printf is being told, go ahead and print out a string that looks like this.', 'start': 2635.699, 'duration': 4.123}], 'summary': 'In c programming, printf requires a format string and an argument to print a specified string.', 'duration': 24.355, 'max_score': 2615.467, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M2615467.jpg'}, {'end': 2820.792, 'src': 'embed', 'start': 2795.015, 'weight': 3, 'content': [{'end': 2801.059, 'text': "Ah, how do you make a distinction between the placeholders if you have different variables? It's the ordering from left to right.", 'start': 2795.015, 'duration': 6.044}, {'end': 2805.482, 'text': "So in this case, it's a trivial example because there's only one variable and one placeholder.", 'start': 2801.359, 'duration': 4.123}, {'end': 2811.326, 'text': 'But if, as you were hinting, I had multiple percent s something something, something, percent s something, something, something,', 'start': 2805.742, 'duration': 5.584}, {'end': 2818.75, 'text': 'I would just make sure that I pass printf the first variable comma, the second variable comma, the third variable and so forth, left to right.', 'start': 2811.326, 'duration': 7.424}, {'end': 2820.792, 'text': 'Other questions? Yeah.', 'start': 2819.871, 'duration': 0.921}], 'summary': 'Making a distinction between placeholders depends on the ordering of variables in printf.', 'duration': 25.777, 'max_score': 2795.015, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M2795015.jpg'}], 'start': 2447.648, 'title': 'User input in scratch and c programming functions', 'summary': 'Covers obtaining user input in scratch using a function and examples of getting names and yes or no responses. it also introduces functions like getstring and printf in c programming, emphasizing naming conventions, string handling, and formatting output strings.', 'chapters': [{'end': 2482.881, 'start': 2447.648, 'title': 'User input in scratch', 'summary': "Discusses the use of a function in scratch to obtain user input, with examples of getting names and yes or no responses, and the concept of returning a value, as demonstrated by the hardcoded variable 'answer'.", 'duration': 35.233, 'highlights': ['The use of a function in Scratch to obtain user input, such as getting names and yes or no responses.', "Demonstration of the concept of returning a value, as illustrated by the hardcoded variable 'answer'.", 'The block used to get the name of someone in lecture and to get yes or no responses in an animation with the gingerbread house.']}, {'end': 2876.056, 'start': 2483.381, 'title': 'C programming: functions and string handling', 'summary': 'Introduces the usage of functions like getstring and printf in c programming, highlighting the conventions for naming functions, handling strings, and formatting output strings with placeholders and multiple variables.', 'duration': 392.675, 'highlights': ['In C, the getString function is used to get input from the user, and the returned value is stored in a variable, with the convention to use underscores in function names.', 'The concept of strings in programming languages is explained as a sequence of characters, and in C, strings are represented within double quotes and can be manipulated using functions like printf for formatting output.', 'The printf function in C requires a format code or format string to specify the type of input, and placeholders like %s are used to substitute variables within the formatted string.', 'The use of multiple placeholders in a formatted string is demonstrated, allowing for the substitution of multiple variables in the output.']}], 'duration': 428.408, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M2447648.jpg', 'highlights': ['Demonstration of using a function in Scratch to obtain user input', 'Explanation of the getString function in C for user input', 'Introduction to formatting output strings using printf in C', 'Illustration of using placeholders in a formatted string for variable substitution', 'Explanation of the concept of strings in programming languages']}, {'end': 3395.841, 'segs': [{'end': 3061.018, 'src': 'embed', 'start': 3031.727, 'weight': 0, 'content': [{'end': 3033.269, 'text': 'which is just to print out the words.', 'start': 3031.727, 'duration': 1.542}, {'end': 3035.151, 'text': 'at the end of the day Hello World.', 'start': 3033.269, 'duration': 1.882}, {'end': 3038.792, 'text': "And we'll tease apart in just a bit what all these various lines are doing.", 'start': 3035.211, 'duration': 3.581}, {'end': 3041.373, 'text': "But the interesting part is what's highlighted in green here.", 'start': 3039.072, 'duration': 2.301}, {'end': 3044.554, 'text': "And this is just one of the features of CS50's sandbox.", 'start': 3041.453, 'duration': 3.101}, {'end': 3049.755, 'text': 'It will color code different concepts within your code so that they just kind of jump out at you.', 'start': 3044.914, 'duration': 4.841}, {'end': 3050.895, 'text': "The colors aren't actually there.", 'start': 3049.835, 'duration': 1.06}, {'end': 3054.376, 'text': "You don't have to color code things yourself.", 'start': 3050.955, 'duration': 3.421}, {'end': 3061.018, 'text': 'It just does it automatically so that you can see the different components, just like MIT colorizes the various scratch puzzle pieces the same.', 'start': 3054.656, 'duration': 6.362}], 'summary': "Cs50's sandbox color codes code components for easier visualization.", 'duration': 29.291, 'max_score': 3031.727, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M3031727.jpg'}, {'end': 3169.259, 'src': 'embed', 'start': 3129.685, 'weight': 4, 'content': [{'end': 3139.868, 'text': "If we have what we'll start calling our source code, which can be written, in our case, in C, but you can write source code in Java, in C++,", 'start': 3129.685, 'duration': 10.183}, {'end': 3141.889, 'text': 'in Python, in dozens of other language.', 'start': 3139.868, 'duration': 2.021}, {'end': 3144.73, 'text': 'Source code is a generic term that just means the code that we humans have written.', 'start': 3141.909, 'duration': 2.821}, {'end': 3151.072, 'text': "We need some way of converting it into 0s and 1s, which henceforth we're just going to call machine code.", 'start': 3145.17, 'duration': 5.902}, {'end': 3152.513, 'text': 'which feels like a reasonable name.', 'start': 3151.232, 'duration': 1.281}, {'end': 3155.054, 'text': "It's the zeros and ones that a machine understands.", 'start': 3152.573, 'duration': 2.481}, {'end': 3157.995, 'text': 'How does a machine know what zeros and ones to understand?', 'start': 3155.354, 'duration': 2.641}, {'end': 3162.857, 'text': "Well, that's the whole reasoning behind having CPUs, central processing units, the brains of a computer.", 'start': 3158.215, 'duration': 4.642}, {'end': 3165.698, 'text': 'They are just hardwired at the factory, so to speak.', 'start': 3163.197, 'duration': 2.501}, {'end': 3169.259, 'text': 'It entails factory to understand certain patterns of zeros and ones.', 'start': 3165.978, 'duration': 3.281}], 'summary': 'Source code can be written in various languages such as c, java, c++, python, etc., and needs to be converted to machine code understood by cpus.', 'duration': 39.574, 'max_score': 3129.685, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M3129685.jpg'}, {'end': 3214.273, 'src': 'embed', 'start': 3185.605, 'weight': 1, 'content': [{'end': 3194.348, 'text': "Other humans have already written programs that we're going to start calling a compiler that allows us to convert source code to machine code.", 'start': 3185.605, 'duration': 8.743}, {'end': 3195.628, 'text': "It's just one additional step.", 'start': 3194.408, 'duration': 1.22}, {'end': 3203.431, 'text': "This step did not exist in Scratch, but we're going to run a program that's generally called a compiler that we pass our program to.", 'start': 3195.669, 'duration': 7.762}, {'end': 3214.273, 'text': 'as input and we get as output machine code, thereby perfectly bringing us full circle to what computer science is in now the context of programming.', 'start': 3205.023, 'duration': 9.25}], 'summary': 'A compiler converts source code to machine code, completing the circle of programming.', 'duration': 28.668, 'max_score': 3185.605, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M3185605.jpg'}, {'end': 3306.64, 'src': 'embed', 'start': 3278.662, 'weight': 2, 'content': [{'end': 3286.486, 'text': "And at first, it might feel like a regression, like why are we giving up all these beautiful amenities of modern on computers, but it's more powerful.", 'start': 3278.662, 'duration': 7.824}, {'end': 3287.807, 'text': "And it's more explicit.", 'start': 3286.707, 'duration': 1.1}, {'end': 3291.55, 'text': 'It lets you do exactly what you want to do by sending commands to the computer.', 'start': 3287.887, 'duration': 3.663}, {'end': 3293.151, 'text': 'So this is my terminal one.', 'start': 3291.89, 'duration': 1.261}, {'end': 3294.972, 'text': 'I can create others just to have multiple windows.', 'start': 3293.191, 'duration': 1.781}, {'end': 3300.296, 'text': 'But this is giving me access to the underlying server that I now have access to.', 'start': 3295.332, 'duration': 4.964}, {'end': 3306.64, 'text': "So if any of you, when it comes time to the first problem set, log into the same tool, you don't all have the same environment.", 'start': 3300.396, 'duration': 6.244}], 'summary': 'Using terminal gives explicit control and unique environments for problem-solving.', 'duration': 27.978, 'max_score': 3278.662, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M3278662.jpg'}, {'end': 3348.424, 'src': 'embed', 'start': 3318.594, 'weight': 5, 'content': [{'end': 3320.577, 'text': "And the way I'm going to do this is like this.", 'start': 3318.594, 'duration': 1.983}, {'end': 3325.966, 'text': 'Clang, which stands for C language, hello.c.', 'start': 3321.298, 'duration': 4.668}, {'end': 3335.15, 'text': "Enter, And the fact that I see nothing happening is actually an amazing thing, because there's an infinite number of things, frankly,", 'start': 3328.143, 'duration': 7.007}, {'end': 3335.791, 'text': 'that can go wrong.', 'start': 3335.15, 'duration': 0.641}, {'end': 3340.816, 'text': 'And the computer will happily yell at you with its cryptic-looking error messages if any of those things do go wrong.', 'start': 3336.011, 'duration': 4.805}, {'end': 3345.481, 'text': 'So seeing nothing but another blinking prompt with a dollar sign is actually a good thing.', 'start': 3341.097, 'duration': 4.384}, {'end': 3348.424, 'text': 'My code has somehow been converted to zeros and ones.', 'start': 3345.842, 'duration': 2.582}], 'summary': "Executing c program 'hello.c' results in no error messages, indicating successful execution.", 'duration': 29.83, 'max_score': 3318.594, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M3318594.jpg'}, {'end': 3408.084, 'src': 'embed', 'start': 3379.634, 'weight': 7, 'content': [{'end': 3382.255, 'text': 'This is a cloud-based Linux environment.', 'start': 3379.634, 'duration': 2.621}, {'end': 3384.216, 'text': 'Linux is a super popular operating system.', 'start': 3382.335, 'duration': 1.881}, {'end': 3387.738, 'text': 'It happens to be used by lots of computer scientists, lots of websites, lots of servers.', 'start': 3384.236, 'duration': 3.502}, {'end': 3395.841, 'text': 'In fact, almost every website you visit these days is powered, if not by Windows, by Linux and variations thereof called Unix and other flavors still.', 'start': 3387.758, 'duration': 8.083}, {'end': 3400.582, 'text': "It's just a very popular and often free operating system that CS50 Sandbox itself uses.", 'start': 3396.341, 'duration': 4.241}, {'end': 3403.883, 'text': 'To run a file called a.out.', 'start': 3401.122, 'duration': 2.761}, {'end': 3408.084, 'text': "that's in this folder, so to speak, even though you don't see a graphical version of it.", 'start': 3403.883, 'duration': 4.201}], 'summary': 'Linux is a widely used, popular operating system, powering most websites and servers, including cs50 sandbox, in a cloud-based environment.', 'duration': 28.45, 'max_score': 3379.634, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M3379634.jpg'}], 'start': 2876.316, 'title': 'Cs50 sandbox and code conversion', 'summary': "Introduces cs50 sandbox, explaining formatting strings in c and the color coding feature, and explores the process of converting source code to machine code using a compiler for languages like c, java, c++, or python, emphasizing the benefits and functionality of cs50 sandbox's user interface.", 'chapters': [{'end': 3092.25, 'start': 2876.316, 'title': 'Cs50 sandbox and formatting strings', 'summary': "Introduces the cs50 sandbox, a cloud-based tool for coding, and explains the formatting of strings in c using printf, with an emphasis on the standardization of coding environment and the color coding feature of cs50's sandbox.", 'duration': 215.934, 'highlights': ['The chapter introduces the CS50 Sandbox, a cloud-based tool for coding, and explains the formatting of strings in C using printf.', "The chapter emphasizes the standardization of coding environment and the color coding feature of CS50's sandbox."]}, {'end': 3222.221, 'start': 3092.51, 'title': 'Converting source code to machine code', 'summary': "Explores the process of converting source code, written in languages like c, java, c++, or python, to machine code using a compiler, which translates human-readable code to machine-understandable zeros and ones, ultimately enabling the computer's central processing unit to execute the instructions.", 'duration': 129.711, 'highlights': ["A compiler allows us to convert source code to machine code, enabling the computer's central processing unit to understand and execute the instructions.", 'Source code, written in languages like C, Java, C++, or Python, needs to be converted to machine code, which comprises zeros and ones that a machine understands.', "Machine code, comprising zeros and ones, is the language understood by the computer's central processing unit, which is hardwired to recognize specific patterns of zeros and ones."]}, {'end': 3395.841, 'start': 3222.221, 'title': 'Cs50 sandbox user interface', 'summary': 'Describes the cs50 sandbox user interface, the use of terminal windows for programming, converting code to zeros and ones, and the storage of compiled files, highlighting the benefits and functionality of the manual approach to coding.', 'duration': 173.62, 'highlights': ['The use of terminal windows for programming provides a more powerful and explicit way to send commands to the computer, allowing individuals to access their own isolated copies of the same software and storage space.', 'Converting code to zeros and ones using Clang, which stands for C language, demonstrates the process of compiling code and storing it in a file called a.out, providing insight into the manual approach to running programs in a cloud-based Linux environment.', 'The benefits of manual coding are highlighted through the demonstration of accessing the underlying server, the storage of compiled files, and the use of a cloud-based Linux environment, emphasizing the power and explicit nature of the approach.']}], 'duration': 519.525, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M2876316.jpg', 'highlights': ['The chapter introduces the CS50 Sandbox, a cloud-based tool for coding, and explains the formatting of strings in C using printf.', "A compiler allows us to convert source code to machine code, enabling the computer's central processing unit to understand and execute the instructions.", 'The use of terminal windows for programming provides a more powerful and explicit way to send commands to the computer, allowing individuals to access their own isolated copies of the same software and storage space.', "The chapter emphasizes the standardization of coding environment and the color coding feature of CS50's sandbox.", 'Source code, written in languages like C, Java, C++, or Python, needs to be converted to machine code, which comprises zeros and ones that a machine understands.', 'Converting code to zeros and ones using Clang, which stands for C language, demonstrates the process of compiling code and storing it in a file called a.out, providing insight into the manual approach to running programs in a cloud-based Linux environment.', "Machine code, comprising zeros and ones, is the language understood by the computer's central processing unit, which is hardwired to recognize specific patterns of zeros and ones.", 'The benefits of manual coding are highlighted through the demonstration of accessing the underlying server, the storage of compiled files, and the use of a cloud-based Linux environment, emphasizing the power and explicit nature of the approach.']}, {'end': 4702.359, 'segs': [{'end': 3588.12, 'src': 'embed', 'start': 3559.397, 'weight': 0, 'content': [{'end': 3564.146, 'text': 'And you can literally type make hello, where hello is the name of the program you want to make.', 'start': 3559.397, 'duration': 4.749}, {'end': 3574.855, 'text': 'This program, whose name is make, will look for a file by default called hello.c, therefore saving you the time of specifying it.', 'start': 3565.069, 'duration': 9.786}, {'end': 3578.297, 'text': 'Hit Enter now, and oh my god, look what it just did.', 'start': 3575.275, 'duration': 3.022}, {'end': 3581.659, 'text': 'It has even more configuration options.', 'start': 3578.317, 'duration': 3.342}, {'end': 3583.638, 'text': 'that are baked into it.', 'start': 3582.637, 'duration': 1.001}, {'end': 3588.12, 'text': 'And we, the CS50 staff, configured CS50 Sandbox to have these various features.', 'start': 3583.698, 'duration': 4.422}], 'summary': "The program 'make' automatically looks for a file called hello.c, saving time and offering configuration options for cs50 sandbox.", 'duration': 28.723, 'max_score': 3559.397, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M3559397.jpg'}, {'end': 3747.495, 'src': 'embed', 'start': 3719.707, 'weight': 4, 'content': [{'end': 3724.371, 'text': 'And frankly, this is where you very quickly get derailed or kind of freaked out because, oh my god, I only wrote two lines of code.', 'start': 3719.707, 'duration': 4.664}, {'end': 3730.096, 'text': 'How do I have 20 lines of errors somehow? So the computer is kind of as confused as you.', 'start': 3724.411, 'duration': 5.685}, {'end': 3735.661, 'text': "And the most important thing when you face this kind of situation where it's just cryptic, erroneous output, start at the top.", 'start': 3730.156, 'duration': 5.505}, {'end': 3740.847, 'text': "Even if your window's kind of small, and therefore a whole bunch of stuff scrolls on the screen quickly, scroll up to the top.", 'start': 3736.141, 'duration': 4.706}, {'end': 3747.495, 'text': "Because odds are, there's one mistake up at the very top and that one mistake just had a cascading effect on the compiler,", 'start': 3740.907, 'duration': 6.588}], 'summary': 'When faced with cryptic errors, start from the top to find the single mistake causing cascading effects.', 'duration': 27.788, 'max_score': 3719.707, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M3719707.jpg'}, {'end': 3872.599, 'src': 'embed', 'start': 3846.196, 'weight': 5, 'content': [{'end': 3850.559, 'text': "We need to do not only include standard IO, which we'll explain in a moment, but also CS50.", 'start': 3846.196, 'duration': 4.363}, {'end': 3853.906, 'text': 'so-called library.', 'start': 3852.805, 'duration': 1.101}, {'end': 3856.768, 'text': 'So CS50 has a lot of humans involved with it.', 'start': 3854.286, 'duration': 2.482}, {'end': 3858.329, 'text': "And over time we've decided you know what?", 'start': 3856.808, 'duration': 1.521}, {'end': 3867.536, 'text': 'We could make the first hour of CS50 a little easier and the on-ramp a little cleaner for folks with no background by just inventing a few features ourselves,', 'start': 3858.689, 'duration': 8.847}, {'end': 3869.557, 'text': 'such as the ability to get strings from the user.', 'start': 3867.536, 'duration': 2.021}, {'end': 3872.599, 'text': 'So it turns out getString is also not a function that comes with C.', 'start': 3869.737, 'duration': 2.862}], 'summary': 'Cs50 introduces new features to ease onboarding, like getstring for user input.', 'duration': 26.403, 'max_score': 3846.196, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M3846196.jpg'}, {'end': 4351.096, 'src': 'embed', 'start': 4305.214, 'weight': 6, 'content': [{'end': 4312.939, 'text': 'So, just to recap, then, with code like this, how many functions have I used in this particular program??', 'start': 4305.214, 'duration': 7.725}, {'end': 4315.981, 'text': 'How many functions?', 'start': 4315.28, 'duration': 0.701}, {'end': 4322.745, 'text': "So it's two printf, which we've been using, and getString, which is the new one.", 'start': 4319.783, 'duration': 2.962}, {'end': 4326.658, 'text': 'Where is getString declared? CS50.', 'start': 4322.925, 'duration': 3.733}, {'end': 4331.023, 'text': 'h, printf, meanwhile, is declared in standard IO.h, standard input output.', 'start': 4326.658, 'duration': 4.365}, {'end': 4335.208, 'text': 'Meanwhile, string, this data type, also comes from CS50 itself.', 'start': 4331.344, 'duration': 3.864}, {'end': 4339.252, 'text': "And then we've used the format codes and we've used variables to achieve the same result.", 'start': 4335.488, 'duration': 3.764}, {'end': 4340.754, 'text': "And let's just hammer this home.", 'start': 4339.472, 'duration': 1.282}, {'end': 4345.912, 'text': 'Brian and Karim, do you mind popping up for just a second? Or who is that? Aaron, come on up.', 'start': 4340.854, 'duration': 5.058}, {'end': 4351.096, 'text': "So just to make this clear, because there's now some terminology that we want to use.", 'start': 4346.733, 'duration': 4.363}], 'summary': 'The program uses 3 functions, including 2 printf and 1 getstring, with relevant declarations and data types.', 'duration': 45.882, 'max_score': 4305.214, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M4305214.jpg'}, {'end': 4419.631, 'src': 'embed', 'start': 4391.92, 'weight': 2, 'content': [{'end': 4395.402, 'text': "And let's focus, though, for just a moment on what the key takeaways are.", 'start': 4391.92, 'duration': 3.482}, {'end': 4396.823, 'text': 'One, functions.', 'start': 4395.802, 'duration': 1.021}, {'end': 4398.443, 'text': 'can take inputs.', 'start': 4397.463, 'duration': 0.98}, {'end': 4401.264, 'text': 'Those inputs are called arguments or parameters.', 'start': 4398.643, 'duration': 2.621}, {'end': 4403.725, 'text': 'And functions can return things.', 'start': 4401.885, 'duration': 1.84}, {'end': 4405.166, 'text': 'They can have return values.', 'start': 4403.865, 'duration': 1.301}, {'end': 4414.849, 'text': "Printf, for instance, does it take inputs? What's the input to printf, for instance? Hello world.", 'start': 4405.586, 'duration': 9.263}, {'end': 4415.049, 'text': 'DAVID J.', 'start': 4414.869, 'duration': 0.18}, {'end': 4415.67, 'text': 'Yeah, like hello world.', 'start': 4415.049, 'duration': 0.621}, {'end': 4419.631, 'text': 'Whatever it is you want to print is, by definition, the input to printf.', 'start': 4415.75, 'duration': 3.881}], 'summary': "Functions can take inputs (arguments/parameters) and return values, such as the input 'hello world' to printf.", 'duration': 27.711, 'max_score': 4391.92, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M4391920.jpg'}, {'end': 4464.612, 'src': 'embed', 'start': 4436.535, 'weight': 7, 'content': [{'end': 4438.997, 'text': "But we've only seen printf for the moment as taking inputs.", 'start': 4436.535, 'duration': 2.462}, {'end': 4440.059, 'text': 'More on that another time.', 'start': 4439.078, 'duration': 0.981}, {'end': 4441.3, 'text': 'Get string, meanwhile.', 'start': 4440.419, 'duration': 0.881}, {'end': 4449.683, 'text': 'Does get string take inputs? How many inputs? Just one, the prompt that you want the human to see.', 'start': 4441.34, 'duration': 8.343}, {'end': 4454.566, 'text': "The first prompt I used was, what is your name? I could make the prompt anything, but that's the question that getString is asking.", 'start': 4449.723, 'duration': 4.843}, {'end': 4457.407, 'text': 'Does getString return a value? It does.', 'start': 4454.606, 'duration': 2.801}, {'end': 4460.849, 'text': "That's, of course, in Scratch called answer, hard coded as answer.", 'start': 4457.588, 'duration': 3.261}, {'end': 4462.711, 'text': 'We can store it in any variable we want.', 'start': 4461.11, 'duration': 1.601}, {'end': 4464.612, 'text': 'So let me just go ahead and implement this program.', 'start': 4462.931, 'duration': 1.681}], 'summary': 'The getstring function takes one input, returns a value, and allows for a customizable prompt.', 'duration': 28.077, 'max_score': 4436.535, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M4436535.jpg'}, {'end': 4615.508, 'src': 'embed', 'start': 4585.553, 'weight': 1, 'content': [{'end': 4589.114, 'text': 'which actually open a can of worms as to problems that can happen in a computer.', 'start': 4585.553, 'duration': 3.561}, {'end': 4597.017, 'text': 'And it turns out you can store different types of variables, not just integers and strings, but bool for Boolean and chars for characters.', 'start': 4589.574, 'duration': 7.443}, {'end': 4598.999, 'text': 'And you can format those things in printf.', 'start': 4597.097, 'duration': 1.902}, {'end': 4601.2, 'text': "We've only seen %s.", 'start': 4599.019, 'duration': 2.181}, {'end': 4604.062, 'text': "I alluded to %i earlier, but there's a few others still.", 'start': 4601.26, 'duration': 2.802}, {'end': 4606.723, 'text': "But we've got a lot of possibilities here.", 'start': 4604.682, 'duration': 2.041}, {'end': 4610.205, 'text': "But let's go ahead and take, say, a five minute break to give everyone a bit of a respite,", 'start': 4606.743, 'duration': 3.462}, {'end': 4615.508, 'text': 'turn on some music and come back in five and dive in deeper to more sophisticated programs in C.', 'start': 4610.205, 'duration': 5.303}], 'summary': 'In c programming, variables can store different types, including bool and chars. more formatting options are available in printf.', 'duration': 29.955, 'max_score': 4585.553, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M4585553.jpg'}, {'end': 4677.455, 'src': 'embed', 'start': 4643.905, 'weight': 3, 'content': [{'end': 4646.167, 'text': "We'll initially in the semester use it for C.", 'start': 4643.905, 'duration': 2.262}, {'end': 4653.193, 'text': "But if you've written Java before, or Python or any number of languages, when you go to sandbox.cs50.io,", 'start': 4646.167, 'duration': 7.026}, {'end': 4655.114, 'text': 'you can simply choose the language you want to write in.', 'start': 4653.193, 'duration': 1.921}, {'end': 4659.698, 'text': "And then at the bottom, you'll see you can specify the name of the file you want to pre-create.", 'start': 4655.454, 'duration': 4.244}, {'end': 4664.002, 'text': 'So for instance, what I did earlier was I selected C at top.', 'start': 4659.918, 'duration': 4.084}, {'end': 4668.186, 'text': 'And then at the bottom, I typed in hello.c, because that was the name of the file I wanted.', 'start': 4664.322, 'duration': 3.864}, {'end': 4669.427, 'text': 'And then I clicked Start.', 'start': 4668.446, 'duration': 0.981}, {'end': 4677.455, 'text': 'And what that led me to was precisely the interface in which we wrote hello.c just a moment ago, where my code editor appears on the top.', 'start': 4669.587, 'duration': 7.868}], 'summary': 'You can choose c, java, or python to write in sandbox.cs50.io and pre-create files.', 'duration': 33.55, 'max_score': 4643.905, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M4643905.jpg'}], 'start': 3396.341, 'title': 'C programming concepts', 'summary': 'Introduces command line environment, debugging errors, and functions in c programming, covering command line arguments, compilation process, make command, custom functions, libraries, function inputs and return values, data types, formatting options in printf, and introduction to cs50 sandbox for programming.', 'chapters': [{'end': 3700.514, 'start': 3396.341, 'title': 'Introduction to command line and compilation', 'summary': 'Introduces the command line environment, command line arguments, compilation process, and the use of make command in c programming, providing insights on how to run and compile programs, automate commands, and take user input.', 'duration': 304.173, 'highlights': ['The chapter introduces the command line environment, command line arguments, compilation process, and the use of make command in C programming.', 'The make command automates the compilation process and saves time by looking for a default file, hello.c, and automating the necessary steps.', 'The use of the get_string function to take user input and store it in a variable for further processing is demonstrated.']}, {'end': 4391.86, 'start': 3701.134, 'title': 'Debugging code and understanding compilation', 'summary': 'Covers debugging errors in code, understanding the compilation process, and utilizing custom functions and libraries in c programming through practical examples and explanations.', 'duration': 690.726, 'highlights': ['Understanding and addressing cryptic error messages by starting at the top of the output', 'Incorporating custom functions from CS50 library to simplify code', 'Utilizing format codes and variables for user input manipulation']}, {'end': 4702.359, 'start': 4391.92, 'title': 'Functions and return values in c', 'summary': 'Explores the concept of functions in c, highlighting their ability to take inputs, called arguments or parameters, and return values, exemplifying with printf and getstring functions, and delves into the possibilities of c programming, including different data types and formatting options in printf, and introduces the cs50 sandbox for programming in multiple languages.', 'duration': 310.439, 'highlights': ['The chapter explains the concept of functions in C, emphasizing their ability to take inputs, called arguments or parameters, and return values.', 'The examples of printf and getString functions illustrate the input and return value aspects of functions in C, providing a clear understanding of their functionality.', 'The chapter introduces the possibilities in C programming, including different data types such as integers, characters, floats, and doubles, along with formatting options in printf.', 'The CS50 Sandbox is introduced as a platform for programming in multiple languages, such as C, Java, and Python, and provides the ability to create and run code in a user-friendly interface.']}], 'duration': 1306.018, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M3396341.jpg', 'highlights': ['The make command automates the compilation process and saves time by looking for a default file, hello.c, and automating the necessary steps.', 'The chapter introduces the possibilities in C programming, including different data types such as integers, characters, floats, and doubles, along with formatting options in printf.', 'The chapter explains the concept of functions in C, emphasizing their ability to take inputs, called arguments or parameters, and return values.', 'The CS50 Sandbox is introduced as a platform for programming in multiple languages, such as C, Java, and Python, and provides the ability to create and run code in a user-friendly interface.', 'Understanding and addressing cryptic error messages by starting at the top of the output', 'Incorporating custom functions from CS50 library to simplify code', 'Utilizing format codes and variables for user input manipulation', 'The use of the get_string function to take user input and store it in a variable for further processing is demonstrated.', 'The examples of printf and getString functions illustrate the input and return value aspects of functions in C, providing a clear understanding of their functionality.']}, {'end': 6110.555, 'segs': [{'end': 4850.958, 'src': 'embed', 'start': 4823.744, 'weight': 1, 'content': [{'end': 4827.685, 'text': "And we'll come back in the weeks to come as to why it's int, why it's main, why it's void.", 'start': 4823.744, 'duration': 3.941}, {'end': 4833.568, 'text': "But for now, humans years ago just decided that when you're writing a program in C and you want to start the program off,", 'start': 4827.886, 'duration': 5.682}, {'end': 4837.69, 'text': 'you literally have to type int main void with those parentheses, with those curly braces.', 'start': 4833.568, 'duration': 4.122}, {'end': 4840.391, 'text': "And it's the equivalent to scratches when green flag clicked.", 'start': 4837.89, 'duration': 2.501}, {'end': 4842.352, 'text': 'But this program will not compile.', 'start': 4840.811, 'duration': 1.541}, {'end': 4845.314, 'text': "And I don't even want to induce the stress of seeing those errors.", 'start': 4842.972, 'duration': 2.342}, {'end': 4850.958, 'text': 'How do I void it? Yeah, I need to teach the computer that get int exists.', 'start': 4845.334, 'duration': 5.624}], 'summary': "In c programming, 'int main void' is used to start a program, resembling 'when green flag clicked' in scratch, but this program won't compile without 'int' and 'get int' needs to be taught to the computer.", 'duration': 27.214, 'max_score': 4823.744, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M4823744.jpg'}, {'end': 4893.151, 'src': 'embed', 'start': 4863.648, 'weight': 7, 'content': [{'end': 4864.689, 'text': 'More on that another time.', 'start': 4863.648, 'duration': 1.041}, {'end': 4866.791, 'text': 'But that just gives us access to printf.', 'start': 4865.11, 'duration': 1.681}, {'end': 4874.263, 'text': "So if I've made no typos, I should be able to compile this program by running what command? Make int.", 'start': 4867.351, 'duration': 6.912}, {'end': 4875.444, 'text': 'I could do clang.', 'start': 4874.403, 'duration': 1.041}, {'end': 4877.205, 'text': 'I could do clang dash o.', 'start': 4875.544, 'duration': 1.661}, {'end': 4883.787, 'text': "But for now, I'm going to do it simpler with just make int and let make automate the process of compiling this program.", 'start': 4877.205, 'duration': 6.582}, {'end': 4885.428, 'text': 'No error messages is good.', 'start': 4884.127, 'duration': 1.301}, {'end': 4886.769, 'text': 'Let me go ahead and zoom in.', 'start': 4885.788, 'duration': 0.981}, {'end': 4889.87, 'text': 'Dot slash int, I think, would run the program.', 'start': 4887.649, 'duration': 2.221}, {'end': 4893.151, 'text': 'Integer, how about 42? Hello, 42.', 'start': 4890.35, 'duration': 2.801}], 'summary': "Using make to compile program, no error messages, running program outputs 'hello, 42'.", 'duration': 29.503, 'max_score': 4863.648, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M4863648.jpg'}, {'end': 5090.441, 'src': 'embed', 'start': 5061.907, 'weight': 0, 'content': [{'end': 5064.688, 'text': 'Let me go ahead and just open this example in advance.', 'start': 5061.907, 'duration': 2.781}, {'end': 5069.43, 'text': "This one's going to be called ints.c, so that I don't have to type everything out.", 'start': 5065.448, 'duration': 3.982}, {'end': 5078.513, 'text': "And in ints.c we're going to see some math written in code that I pre-created just to reinforce that you can actually do some basic arithmetic in a program.", 'start': 5069.85, 'duration': 8.663}, {'end': 5081.174, 'text': 'I can see more of the code here by just scrolling down.', 'start': 5078.573, 'duration': 2.601}, {'end': 5083.895, 'text': 'And let me scroll this up so we can focus on main.', 'start': 5081.754, 'duration': 2.141}, {'end': 5086.036, 'text': 'And let me zoom in on the first few lines.', 'start': 5084.195, 'duration': 1.841}, {'end': 5090.441, 'text': "On this first line, I'm just getting an int, and I'm calling it x.", 'start': 5086.776, 'duration': 3.665}], 'summary': 'Demonstration of basic arithmetic in a pre-created code file called ints.c', 'duration': 28.534, 'max_score': 5061.907, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M5061907.jpg'}, {'end': 5130.72, 'src': 'embed', 'start': 5101.934, 'weight': 5, 'content': [{'end': 5107.34, 'text': 'These lines in green are just some format strings, just what do I want printf to display.', 'start': 5101.934, 'duration': 5.406}, {'end': 5114.288, 'text': 'I literally, in this highlighted line here, want printf to display x plus y equals something.', 'start': 5107.661, 'duration': 6.627}, {'end': 5117.271, 'text': "What is that something? Well, notice what's cool about printf.", 'start': 5114.688, 'duration': 2.583}, {'end': 5123.135, 'text': 'is that before it is passed in input, you can perform simple arithmetic operations.', 'start': 5118.052, 'duration': 5.083}, {'end': 5130.72, 'text': 'So if you want to add x and y together, literally do x plus y, then the sum of those numbers is what will get handed to printf as its input.', 'start': 5123.155, 'duration': 7.565}], 'summary': 'Printf can perform simple arithmetic operations before being passed input, allowing the addition of x and y together.', 'duration': 28.786, 'max_score': 5101.934, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M5101934.jpg'}, {'end': 5343.508, 'src': 'embed', 'start': 5319.929, 'weight': 8, 'content': [{'end': 5326.415, 'text': "And that's going to give me this example, which is implemented using floating point values instead.", 'start': 5319.929, 'duration': 6.486}, {'end': 5329.658, 'text': "So once this loads, I'm going to see a program I wrote in advance.", 'start': 5327.356, 'duration': 2.302}, {'end': 5333.221, 'text': "It's a little shorter, because now I only care about looking at one problem.", 'start': 5329.698, 'duration': 3.523}, {'end': 5335.623, 'text': 'And notice now, x and y are now floating.', 'start': 5333.581, 'duration': 2.042}, {'end': 5337.964, 'text': 'and not ints, another data type that exists.', 'start': 5335.723, 'duration': 2.241}, {'end': 5340.486, 'text': "And I'm using get float, which also comes from CS50's library.", 'start': 5338.024, 'duration': 2.462}, {'end': 5343.508, 'text': 'And then this line is almost the same.', 'start': 5340.906, 'duration': 2.602}], 'summary': "Program uses floating point values instead of integers, utilizing cs50's library.", 'duration': 23.579, 'max_score': 5319.929, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M5319929.jpg'}, {'end': 5570.383, 'src': 'embed', 'start': 5545.833, 'weight': 2, 'content': [{'end': 5554.816, 'text': 'That is a problem if you want to represent all possible numbers in the universe, which is infinitely many, with a finite amount of hardware.', 'start': 5545.833, 'duration': 8.983}, {'end': 5559.558, 'text': "So at some point, the computer's got to start cutting some corners.", 'start': 5555.436, 'duration': 4.122}, {'end': 5567.321, 'text': "And so what you're really seeing here is as close as the computer can get to storing that fraction for you precisely.", 'start': 5559.858, 'duration': 7.463}, {'end': 5568.422, 'text': 'And I got a little greedy.', 'start': 5567.481, 'duration': 0.941}, {'end': 5570.383, 'text': 'I looked a little too far to the right.', 'start': 5568.482, 'duration': 1.901}], 'summary': 'Computers struggle to represent infinite numbers precisely.', 'duration': 24.55, 'max_score': 5545.833, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M5545833.jpg'}, {'end': 5663.396, 'src': 'embed', 'start': 5618.432, 'weight': 3, 'content': [{'end': 5623.314, 'text': "because I'm going to literally have to remember or write down or figure out this value and compare against that,", 'start': 5618.432, 'duration': 4.882}, {'end': 5625.795, 'text': 'and not just compare more loosely against 0.2..', 'start': 5623.314, 'duration': 2.481}, {'end': 5626.315, 'text': "And that's true.", 'start': 5625.795, 'duration': 0.52}, {'end': 5630.496, 'text': 'You should actually never compare floating point values in code for equality.', 'start': 5626.575, 'duration': 3.921}, {'end': 5636.258, 'text': "I could probably get away with less than or greater than, but even then, it's going to be a little off from what I expect.", 'start': 5630.976, 'duration': 5.282}, {'end': 5640.089, 'text': 'Why else might this imprecision be worrisome?', 'start': 5638.066, 'duration': 2.023}, {'end': 5646.199, 'text': 'When might you not want your computer being imprecise?', 'start': 5643.515, 'duration': 2.684}, {'end': 5647.32, 'text': 'What domains?', 'start': 5646.579, 'duration': 0.741}, {'end': 5649.063, 'text': 'What worlds outside of a classroom?', 'start': 5647.361, 'duration': 1.702}, {'end': 5651.207, 'text': "Yeah?. What's that??", 'start': 5649.083, 'duration': 2.124}, {'end': 5652.37, 'text': 'DAVID J.', 'start': 5652.21, 'duration': 0.16}, {'end': 5661.515, 'text': "Yeah, so rockets, right? Anything involving math and physics and danger, you don't want numbers to be ever so slightly off.", 'start': 5652.37, 'duration': 9.145}, {'end': 5663.396, 'text': 'And if you think about it, rockets is a good example.', 'start': 5661.555, 'duration': 1.841}], 'summary': 'Comparing floating point values in code for equality can cause imprecision, posing risks in domains like rockets and other math and physics-related fields.', 'duration': 44.964, 'max_score': 5618.432, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M5618432.jpg'}, {'end': 5836.341, 'src': 'embed', 'start': 5810.03, 'weight': 4, 'content': [{'end': 5815.273, 'text': "Any questions, then, about this? We'll come back as to some implications.", 'start': 5810.03, 'duration': 5.243}, {'end': 5815.493, 'text': 'Yeah, here.', 'start': 5815.293, 'duration': 0.2}, {'end': 5821.355, 'text': "So would it always be better to use doubles because they're more precise? DAVID MALANI- Good question.", 'start': 5815.513, 'duration': 5.842}, {'end': 5825.017, 'text': "Would it always be better to use doubles because they're more precise? Short answer, yes.", 'start': 5821.495, 'duration': 3.522}, {'end': 5829.398, 'text': "But we're going to see thematically in this course, in computer science more generally, there's always a trade-off.", 'start': 5825.297, 'duration': 4.101}, {'end': 5833.48, 'text': 'And yes, if you use a double, you will avoid this problem a bit more.', 'start': 5829.658, 'duration': 3.822}, {'end': 5836.341, 'text': 'But what price will you pay, so to speak? Processing power.', 'start': 5833.92, 'duration': 2.421}], 'summary': "Using doubles is more precise, but there's a trade-off with processing power.", 'duration': 26.311, 'max_score': 5810.03, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M5810030.jpg'}, {'end': 6078.671, 'src': 'heatmap', 'start': 5995.26, 'weight': 1, 'content': [{'end': 5998.883, 'text': 'Let me zoom in and do dot slash conditions, Enter.', 'start': 5995.26, 'duration': 3.623}, {'end': 6001.124, 'text': 'x will be, say, 2 again.', 'start': 5999.563, 'duration': 1.561}, {'end': 6003.145, 'text': 'y will be 10.', 'start': 6001.584, 'duration': 1.561}, {'end': 6004.506, 'text': 'x is indeed less than y.', 'start': 6003.145, 'duration': 1.361}, {'end': 6011.59, 'text': "If I run it again, and I can save time by hitting up through my history and just hitting Enter, let's do 2 and 2.", 'start': 6004.506, 'duration': 7.084}, {'end': 6013.531, 'text': 'And indeed, x is equal to y, and so forth.', 'start': 6011.59, 'duration': 1.941}, {'end': 6018.233, 'text': 'So again, just the exact same kind of code as before, but now in the context of a working program.', 'start': 6013.571, 'duration': 4.662}, {'end': 6026.318, 'text': 'What if I actually wanted to get user input, kind of like our past student did with getting yes or no answers to the apple and the cupcake question?', 'start': 6018.574, 'duration': 7.744}, {'end': 6035.903, 'text': 'Well, in answer.c It turns out you can actually get textual input from the user, perhaps a simple yes or no, or just y or n for succinctness.', 'start': 6026.378, 'duration': 9.525}, {'end': 6040.746, 'text': "And in this case, if I just get back a single character, turns out there's a separate data type for character.", 'start': 6036.183, 'duration': 4.563}, {'end': 6046.029, 'text': "If you don't want a whole string, like a whole word or a paragraph or sentence or whatever, you just want one character.", 'start': 6040.786, 'duration': 5.243}, {'end': 6048.61, 'text': "you can actually use what's called a char or character.", 'start': 6046.029, 'duration': 2.581}, {'end': 6051.192, 'text': "And so here, I'm using one other function.", 'start': 6048.99, 'duration': 2.202}, {'end': 6054.274, 'text': 'appropriately named, called get char.', 'start': 6051.952, 'duration': 2.322}, {'end': 6059.558, 'text': "I'm storing it in a variable called c, because it's nice and succinct, of type char.", 'start': 6054.754, 'duration': 4.804}, {'end': 6061.099, 'text': 'And then notice this.', 'start': 6060.219, 'duration': 0.88}, {'end': 6067.665, 'text': "You might not have seen this syntax before, especially if you've never programmed before, even in Scratch,", 'start': 6062.26, 'duration': 5.405}, {'end': 6070.347, 'text': 'but you might have seen this block similar to this in Scratch.', 'start': 6067.665, 'duration': 2.682}, {'end': 6075.629, 'text': "What does the vertical double bar probably imply here? Or, that's it.", 'start': 6070.807, 'duration': 4.822}, {'end': 6077.33, 'text': "So in Scratch, it's nice and user friendly.", 'start': 6075.81, 'duration': 1.52}, {'end': 6078.671, 'text': 'They literally just say OR.', 'start': 6077.35, 'duration': 1.321}], 'summary': 'Introduction to using conditions and getting user input in a working program.', 'duration': 83.411, 'max_score': 5995.26, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M5995260.jpg'}, {'end': 6046.029, 'src': 'embed', 'start': 6018.574, 'weight': 9, 'content': [{'end': 6026.318, 'text': 'What if I actually wanted to get user input, kind of like our past student did with getting yes or no answers to the apple and the cupcake question?', 'start': 6018.574, 'duration': 7.744}, {'end': 6035.903, 'text': 'Well, in answer.c It turns out you can actually get textual input from the user, perhaps a simple yes or no, or just y or n for succinctness.', 'start': 6026.378, 'duration': 9.525}, {'end': 6040.746, 'text': "And in this case, if I just get back a single character, turns out there's a separate data type for character.", 'start': 6036.183, 'duration': 4.563}, {'end': 6046.029, 'text': "If you don't want a whole string, like a whole word or a paragraph or sentence or whatever, you just want one character.", 'start': 6040.786, 'duration': 5.243}], 'summary': 'Using answer.c, you can get textual input from the user, such as a single character for yes or no.', 'duration': 27.455, 'max_score': 6018.574, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M6018574.jpg'}], 'start': 4702.439, 'title': 'C programming fundamentals and precision', 'summary': 'Introduces c programming basics, demonstrates implementation of programs with floating point values, and explores the limitations of computer memory in representing numbers. it also discusses the implications of imprecision in computing, including its effects on financial and scientific operations, and explains the trade-offs in using different data types and operators.', 'chapters': [{'end': 4922.71, 'start': 4702.439, 'title': 'Introduction to c programming', 'summary': 'Introduces the basics of c programming, including utilizing standard input/output functions, defining main function, and utilizing cs50 library, ending with successful compilation and execution of a program to take and print an integer input.', 'duration': 220.271, 'highlights': ['The program demonstrates the use of get_int function to retrieve an integer input from the user, and printf function to display the input, showcasing the practical application of these concepts in C programming.', "The significance of int main void in C programming is explained, drawing an analogy to the 'when green flag clicked' event in Scratch, and the necessity of including the CS50 library is emphasized to access standard functions like printf and get_int.", "The process of compiling the program using the 'make' command and running it to receive and display integer inputs is explained, demonstrating the execution of a C program in a Linux environment."]}, {'end': 5441.223, 'start': 4922.77, 'title': 'Implementing programs with floating point values', 'summary': 'Covers the implementation of programs using floating point values, illustrating the difference between integer and floating point arithmetic and demonstrating the use of printf, get float, and basic arithmetic operations in c programming.', 'duration': 518.453, 'highlights': ['The chapter demonstrates creating files and implementing programs using floating point values, highlighting the difference between integer and floating point arithmetic and the use of printf and get float in C programming.', 'Explanation of floating point values and their representation in computer programming, emphasizing the ability to store decimal points and the precision of numbers after the decimal point in floating point values.', 'Illustration of basic arithmetic operations in C programming, such as addition, subtraction, multiplication, division, and modular arithmetic, including examples and explanations of their usage.', 'Demonstration of the use of printf to display arithmetic operations in C programming, showcasing the ability to perform simple arithmetic operations before passing input to printf.', 'Comparison of implementing programs using integer and floating point values, highlighting the limitations of integer arithmetic and the need for changes to perform floating point arithmetic in C programming.']}, {'end': 5680.766, 'start': 5441.243, 'title': 'Computer memory and precision', 'summary': 'Discusses the limitations of representing infinite numbers with finite computer memory, the implications of imprecision, and the potential risks in real-world applications, including rockets, due to the finite precision of computer memory.', 'duration': 239.523, 'highlights': ["The computer's finite memory struggles to represent infinite numbers, leading to imprecision in storing values, as seen in the example of representing 2 divided by 10.", 'Imprecision in computer memory can pose significant problems in real-world applications like rockets, where even slight inaccuracies can have serious consequences in math and physics-based operations.', 'Storing data in RAM (random access memory) on computers allows for temporary storage of programs and files while the computer is powered on, with hard disk space serving as permanent storage for files.', 'Comparing floating point values for equality in code can be problematic due to the imprecision of computer memory, leading to potential issues in software development and real-world applications.']}, {'end': 6110.555, 'start': 5680.806, 'title': 'Imprecision in computing', 'summary': 'Discusses the issues of imprecision in computing, highlighting how it affects financial and scientific operations, and the trade-offs involved in using float and double data types, with an emphasis on the implications and the trade-offs in processing power and space. it also explains the concept of parity and demonstrates how to check for even or odd numbers using modulus operation. furthermore, it illustrates the use of character data type and logical operators in a program to handle text input from the user.', 'duration': 429.749, 'highlights': ['The chapter discusses the issues of imprecision in computing, highlighting how it affects financial and scientific operations.', 'The chapter explains the trade-offs involved in using float and double data types, emphasizing the implications and the trade-offs in processing power and space.', 'The chapter demonstrates the concept of parity and how to check for even or odd numbers using modulus operation.', 'The chapter illustrates the use of character data type and logical operators in a program to handle text input from the user.']}], 'duration': 1408.116, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M4702439.jpg', 'highlights': ['The program demonstrates the use of get_int function to retrieve an integer input from the user, showcasing practical application in C programming.', "The significance of int main void in C programming is explained, drawing an analogy to the 'when green flag clicked' event in Scratch.", "The computer's finite memory struggles to represent infinite numbers, leading to imprecision in storing values.", 'The chapter discusses the issues of imprecision in computing, highlighting how it affects financial and scientific operations.', 'The chapter explains the trade-offs involved in using float and double data types, emphasizing the implications and the trade-offs in processing power and space.', 'Demonstration of the use of printf to display arithmetic operations in C programming, showcasing the ability to perform simple arithmetic operations before passing input to printf.', 'Comparing floating point values for equality in code can be problematic due to the imprecision of computer memory, leading to potential issues in software development and real-world applications.', "The process of compiling the program using the 'make' command and running it to receive and display integer inputs is explained, demonstrating the execution of a C program in a Linux environment.", 'The chapter demonstrates creating files and implementing programs using floating point values, highlighting the difference between integer and floating point arithmetic and the use of printf and get float in C programming.', 'The chapter illustrates the use of character data type and logical operators in a program to handle text input from the user.']}, {'end': 7082.227, 'segs': [{'end': 6186.798, 'src': 'embed', 'start': 6158.476, 'weight': 2, 'content': [{'end': 6162.938, 'text': "The moment you start copying and pasting, you're probably not writing good code.", 'start': 6158.476, 'duration': 4.462}, {'end': 6164.278, 'text': "It's not very maintainable.", 'start': 6163.258, 'duration': 1.02}, {'end': 6167.939, 'text': 'Now if I want to change the word or translate it to another language, I have to change it in three places.', 'start': 6164.358, 'duration': 3.581}, {'end': 6170.059, 'text': 'We already decided last week that was bad.', 'start': 6168.199, 'duration': 1.86}, {'end': 6177.867, 'text': 'So what would be better in C or in Scratch or in general than this approach? Yeah, so like a for loop.', 'start': 6170.78, 'duration': 7.087}, {'end': 6178.468, 'text': 'So let me do that.', 'start': 6177.887, 'duration': 0.581}, {'end': 6179.629, 'text': 'Let me create another file.', 'start': 6178.488, 'duration': 1.141}, {'end': 6181.251, 'text': "I'm going to call this one cough1.", 'start': 6180.03, 'duration': 1.221}, {'end': 6183.274, 'text': "c It's my second version.", 'start': 6181.251, 'duration': 2.023}, {'end': 6186.798, 'text': 'Let me go ahead now and just copy and paste the original code.', 'start': 6183.694, 'duration': 3.104}], 'summary': 'Copying and pasting code makes it less maintainable, requiring changes in multiple places. using a for loop is a better approach.', 'duration': 28.322, 'max_score': 6158.476, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M6158476.jpg'}, {'end': 6484.949, 'src': 'embed', 'start': 6456.035, 'weight': 0, 'content': [{'end': 6457.636, 'text': "And frankly, that's kind of good style.", 'start': 6456.035, 'duration': 1.601}, {'end': 6460.356, 'text': 'If main is the most important function in your program,', 'start': 6458.136, 'duration': 2.22}, {'end': 6466.738, 'text': "by default because it is the main function and it's what gets called per earlier by default by the computer,", 'start': 6460.356, 'duration': 6.382}, {'end': 6471.08, 'text': 'why am I going to push it all the way down just to work around this stupid detail?', 'start': 6466.738, 'duration': 4.342}, {'end': 6476.141, 'text': 'Well, I just need to teach the computer what the function is.', 'start': 6471.68, 'duration': 4.461}, {'end': 6478.622, 'text': 'And I can do that a little redundantly.', 'start': 6476.281, 'duration': 2.341}, {'end': 6481.166, 'text': 'by just saying this.', 'start': 6480.185, 'duration': 0.981}, {'end': 6484.949, 'text': "This is what we're going to call the prototype for a function.", 'start': 6481.846, 'duration': 3.103}], 'summary': 'Teaching the computer the function prototype redundantly can be good style.', 'duration': 28.914, 'max_score': 6456.035, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M6456035.jpg'}, {'end': 6557.482, 'src': 'embed', 'start': 6527.75, 'weight': 1, 'content': [{'end': 6529.031, 'text': 'What is in CS50 dot H??', 'start': 6527.75, 'duration': 1.281}, {'end': 6534.691, 'text': "those kinds of we'll call them declarations.", 'start': 6532.27, 'duration': 2.421}, {'end': 6545.056, 'text': "So literally, in standardio.h is a line of code that teaches the computer what printf's inputs are and what printf's output is, if any.", 'start': 6534.851, 'duration': 10.205}, {'end': 6545.886, 'text': 'In cs50.', 'start': 6545.336, 'duration': 0.55}, {'end': 6551.699, 'text': "h, there's literally a line of code that tells the computer what get string's input is and what its output is.", 'start': 6545.886, 'duration': 5.813}, {'end': 6555.201, 'text': 'And the same for get int and get float and get char and others.', 'start': 6551.819, 'duration': 3.382}, {'end': 6557.482, 'text': "That's all that's in those header files.", 'start': 6555.721, 'duration': 1.761}], 'summary': 'Cs50.h contains declarations for input and output functions like printf, get string, get int, get float, and get char.', 'duration': 29.732, 'max_score': 6527.75, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M6527750.jpg'}, {'end': 6849.671, 'src': 'embed', 'start': 6819.313, 'weight': 4, 'content': [{'end': 6820.493, 'text': 'And a do while loop.', 'start': 6819.313, 'duration': 1.18}, {'end': 6824.314, 'text': 'while it sounds obviously similar to a while loop, what seems a little different?', 'start': 6820.493, 'duration': 3.821}, {'end': 6831.116, 'text': 'When I had that forever block earlier translated to while true, what was the order of operations?', 'start': 6824.914, 'duration': 6.202}, {'end': 6835.901, 'text': 'Did we check the condition, the true, and then print hello world?', 'start': 6832.418, 'duration': 3.483}, {'end': 6838.463, 'text': 'Or did we just print hello world and then check the condition??', 'start': 6836.021, 'duration': 2.442}, {'end': 6843.006, 'text': 'Yeah, you might not recall precisely, but I did actually.', 'start': 6840.564, 'duration': 2.442}, {'end': 6846.129, 'text': 'I checked, is true true? And we all said yes, obviously.', 'start': 6843.086, 'duration': 3.043}, {'end': 6849.671, 'text': 'Printf, is it true? Printf, is it true? Printf.', 'start': 6846.589, 'duration': 3.082}], 'summary': 'Comparison of do while loop and while loop, with emphasis on order of operations and confirmation of true condition.', 'duration': 30.358, 'max_score': 6819.313, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M6819313.jpg'}], 'start': 6110.575, 'title': 'C programming functions and loops', 'summary': 'Covers creating functions, function prototypes, and declarations in c, along with introducing the do while loop and discussing the concept of variable scope. it includes examples and highlights the importance of function declaration order and avoiding scope-related issues when declaring variables.', 'chapters': [{'end': 6437.469, 'start': 6110.575, 'title': 'Creating functions in c', 'summary': 'Discusses creating functions in c, starting with copying and pasting code, improving it using a for loop, and then abstracting the code into a new function, encountering errors and understanding the importance of function declaration order in c programming.', 'duration': 326.894, 'highlights': ['The chapter discusses the process of improving code in C, starting with copying and pasting code, then using a for loop to enhance it, and finally abstracting the code into a new function to make it more maintainable and readable.', 'The importance of function declaration order in C programming is highlighted, as the transcript explains the error caused by trying to use a function before it was declared in the file, emphasizing the significance of teaching the computer what a function is before using it.', 'The design decision of creating a new function in C to improve code maintainability and readability is demonstrated, showcasing the process of creating a function to abstract the code and make it reusable for multiple calls.']}, {'end': 6795.684, 'start': 6437.869, 'title': 'Function prototypes and declarations', 'summary': 'Discusses the importance of function prototypes, declaration and their role in teaching the computer about functions, with examples of standard i/o and cs50.h, and the creation of a new function getpositiveint.', 'duration': 357.815, 'highlights': ['The main function should be at the top for good style, as it is the most important function in the program and gets called by default by the computer.', 'Using function prototypes is a conventional way to solve the problem of pushing the main function down, as it provides enough information for the computer to call the function even if the implementation comes later.', 'Header files like standardio.h and cs50.h contain declarations that teach the computer about the inputs and outputs of functions like printf, get string, get int, get float, and get char.', 'Creating a new function getPositiveInt allows for the creation of a function that returns a positive integer, with a user-defined prompt.']}, {'end': 7082.227, 'start': 6796.344, 'title': 'Introduction to do while loop and variable scope', 'summary': 'Introduces the do while loop in c programming and explains the concept of variable scope, highlighting how to use the loop and avoid scope-related issues when declaring variables.', 'duration': 285.883, 'highlights': ['The chapter introduces the do while loop, an alternate looping construct, and explains its functionality, emphasizing the order of operations and its use in executing a block of code at least once.', 'The concept of variable scope is explained, highlighting the limited existence of variables within the curly braces where they are declared, and the solution of declaring variables without assigning a value to make them accessible throughout the program.']}], 'duration': 971.652, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M6110575.jpg', 'highlights': ['The importance of function declaration order in C programming is highlighted, emphasizing the significance of teaching the computer what a function is before using it.', 'Header files like standardio.h and cs50.h contain declarations that teach the computer about the inputs and outputs of functions like printf, get string, get int, get float, and get char.', 'The chapter discusses the process of improving code in C, starting with copying and pasting code, then using a for loop to enhance it, and finally abstracting the code into a new function to make it more maintainable and readable.', 'The main function should be at the top for good style, as it is the most important function in the program and gets called by default by the computer.', 'The chapter introduces the do while loop, an alternate looping construct, and explains its functionality, emphasizing the order of operations and its use in executing a block of code at least once.']}, {'end': 7993.918, 'segs': [{'end': 7286.375, 'src': 'embed', 'start': 7262.499, 'weight': 6, 'content': [{'end': 7269.323, 'text': "And if we're only using, as a matter of convention, 32 bits to represent things, or 64 bits, maybe if we use doubles or something else called a long,", 'start': 7262.499, 'duration': 6.824}, {'end': 7273.046, 'text': 'a long is a 64-bit integer, whereas an integer is typically 32 bits.', 'start': 7269.323, 'duration': 3.723}, {'end': 7282.912, 'text': "It seems that at some point, numbers might overflow, and we're going to actually have some, so to speak, imprecision, ergo integer overflow.", 'start': 7274.547, 'duration': 8.365}, {'end': 7286.375, 'text': 'So you can actually see this or defenses against this in the real world.', 'start': 7283.292, 'duration': 3.083}], 'summary': 'Using 32 or 64 bits for representation may lead to integer overflow, causing imprecision.', 'duration': 23.876, 'max_score': 7262.499, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M7262499.jpg'}, {'end': 7328.132, 'src': 'embed', 'start': 7303.766, 'weight': 4, 'content': [{'end': 7309.567, 'text': "What's the highest score, apparently, according to the screenshot from whoever took this after playing for too many hours? Wasn't me.", 'start': 7303.766, 'duration': 5.801}, {'end': 7312.088, 'text': '4 billion.', 'start': 7311.528, 'duration': 0.56}, {'end': 7312.908, 'text': 'DAVID J.', 'start': 7312.108, 'duration': 0.8}, {'end': 7313.368, 'text': '4 million.', 'start': 7312.928, 'duration': 0.44}, {'end': 7314.069, 'text': 'No, 4 billion.', 'start': 7313.388, 'duration': 0.681}, {'end': 7314.589, 'text': '4 billion.', 'start': 7314.089, 'duration': 0.5}, {'end': 7315.649, 'text': 'Why is that??', 'start': 7314.709, 'duration': 0.94}, {'end': 7323.151, 'text': "Well, it turns out that if numbers in computers, as I've proposed, are generally stored using 32 bits, that kind of invites the question well,", 'start': 7315.949, 'duration': 7.202}, {'end': 7324.871, 'text': 'how high can you count with 32 bits?', 'start': 7323.151, 'duration': 1.72}, {'end': 7328.132, 'text': 'Well, 32 bits means you have 32 zeros and ones.', 'start': 7324.951, 'duration': 3.181}], 'summary': 'Highest score reached in a game: 4 billion, explained by 32-bit storage limit.', 'duration': 24.366, 'max_score': 7303.766, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M7303766.jpg'}, {'end': 7564.306, 'src': 'embed', 'start': 7531.908, 'weight': 2, 'content': [{'end': 7533.97, 'text': 'So what actually happened? Control-C will cancel this.', 'start': 7531.908, 'duration': 2.062}, {'end': 7540.435, 'text': "What happened? I mean, the program's trying to tell me, even though it's a little cryptic, signed integer overflow.", 'start': 7534.57, 'duration': 5.865}, {'end': 7542.736, 'text': 'Signed just means it went from positive to negative, essentially.', 'start': 7540.475, 'duration': 2.261}, {'end': 7547.872, 'text': "So what happened? What's that? Yeah, I ran out of bits.", 'start': 7543.016, 'duration': 4.856}, {'end': 7549.633, 'text': "I'm doubling the number again and again and again.", 'start': 7547.912, 'duration': 1.721}, {'end': 7552.155, 'text': 'And at some point, we carried the 1, so to speak.', 'start': 7549.673, 'duration': 2.482}, {'end': 7556.479, 'text': 'And it was a 33rd 1, therefore past the boundaries of a 32-bit value.', 'start': 7552.275, 'duration': 4.204}, {'end': 7558.681, 'text': 'And it just rolled over to apparently a negative,', 'start': 7556.699, 'duration': 1.982}, {'end': 7564.306, 'text': "because at some point and we haven't talked about it you can use the leftmost bit in some sense to say positive or negative.", 'start': 7558.681, 'duration': 5.625}], 'summary': 'Signed integer overflow occurred due to exceeding 32-bit value, leading to a negative roll-over.', 'duration': 32.398, 'max_score': 7531.908, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M7531908.jpg'}, {'end': 7595.585, 'src': 'embed', 'start': 7570.929, 'weight': 1, 'content': [{'end': 7578.693, 'text': "So if you don't write code to handle this situation and make sure that your numbers are less than 4 billion before you roll over,", 'start': 7570.929, 'duration': 7.764}, {'end': 7579.893, 'text': 'just bugs will happen.', 'start': 7578.693, 'duration': 1.2}, {'end': 7583.975, 'text': 'And this might seem contrived here, but this happened not too long ago.', 'start': 7580.153, 'duration': 3.822}, {'end': 7590.898, 'text': 'So 1999 was just before a lot of people thought the world was going to end because of the so-called Y2K bug.', 'start': 7584.675, 'duration': 6.223}, {'end': 7595.585, 'text': "And it really wasn't so much a bug as it was lack of forethought or lack of features.", 'start': 7591.198, 'duration': 4.387}], 'summary': 'Handling numbers over 4 billion is crucial to avoid bugs, exemplified by the y2k issue.', 'duration': 24.656, 'max_score': 7570.929, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M7570929.jpg'}, {'end': 7730.217, 'src': 'embed', 'start': 7704.64, 'weight': 0, 'content': [{'end': 7710.764, 'text': 'A 787 airplane that has been powered continuously for 248 days, it turns out,', 'start': 7704.64, 'duration': 6.124}, {'end': 7717.709, 'text': 'was the warning can lose all of its electrical power due to the generator going into failsafe mode.', 'start': 7710.764, 'duration': 6.945}, {'end': 7726.434, 'text': 'Why is that? This condition is caused by a software counter internal to the generator that will overflow after 248 days of continuous power.', 'start': 7718.369, 'duration': 8.065}, {'end': 7730.217, 'text': 'So translate that.', 'start': 7729.116, 'duration': 1.101}], 'summary': '787 airplane powered for 248 days faces electrical power loss due to generator software issue.', 'duration': 25.577, 'max_score': 7704.64, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M7704640.jpg'}, {'end': 7897.271, 'src': 'embed', 'start': 7865.196, 'weight': 3, 'content': [{'end': 7867.897, 'text': "It turns out it's 255, if you actually do out all the math.", 'start': 7865.196, 'duration': 2.701}, {'end': 7875.6, 'text': "So it turns out that this game, Civilization, was using a single byte to represent every character's level of aggressiveness in the game.", 'start': 7868.357, 'duration': 7.243}, {'end': 7880.923, 'text': "And Gandhi's was, as you would expect, by default, initialized to 1, like very non-aggressive.", 'start': 7875.96, 'duration': 4.963}, {'end': 7888.638, 'text': 'Unfortunately, in this game of Civilization, When a player adopts democracy in his or her civilization,', 'start': 7881.423, 'duration': 7.215}, {'end': 7891.145, 'text': 'their aggression would be automatically reduced by two.', 'start': 7888.638, 'duration': 2.507}, {'end': 7897.271, 'text': "And so if Gandhi went democratic, his aggression wouldn't go to negative 1.", 'start': 7892.99, 'duration': 4.281}], 'summary': "In the game civilization, gandhi's aggression level was 1, but when he adopted democracy, it reduced by 2 to -1.", 'duration': 32.075, 'max_score': 7865.196, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M7865196.jpg'}, {'end': 7937.654, 'src': 'embed', 'start': 7911.094, 'weight': 5, 'content': [{'end': 7918.216, 'text': "And if you start to keep an eye out in the popular media or when there are bugs or hacks or exploits, it's so often because programming,", 'start': 7911.094, 'duration': 7.122}, {'end': 7921.639, 'text': 'A programmer has made a mistake in his or her code.', 'start': 7919.197, 'duration': 2.442}, {'end': 7922.96, 'text': "They didn't anticipate a scenario.", 'start': 7921.679, 'duration': 1.281}, {'end': 7929.246, 'text': "Or they made maybe reasonable decisions years ago, but that eventually proved to be naive in that we're still running the same code.", 'start': 7923.02, 'duration': 6.226}, {'end': 7930.207, 'text': 'Numbers are getting too big.', 'start': 7929.286, 'duration': 0.921}, {'end': 7931.568, 'text': 'Their math is wrong.', 'start': 7930.247, 'duration': 1.321}, {'end': 7933.27, 'text': 'And so very real things happen.', 'start': 7931.869, 'duration': 1.401}, {'end': 7937.654, 'text': "But what's most important for us is just understanding how and why those things happen.", 'start': 7933.29, 'duration': 4.364}], 'summary': 'Programming mistakes lead to bugs, hacks, and exploits due to miscalculations or outdated code.', 'duration': 26.56, 'max_score': 7911.094, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M7911094.jpg'}], 'start': 7083.223, 'title': 'Integer overflow in computing', 'summary': 'Covers integer overflow and binary arithmetic, demonstrating the consequences of adding 1 to the maximum value of integers, limitations of 32-bit integers, and real-world examples such as the y2k bug and a boeing 787 grounding. it also highlights the impact of programming bugs in the game civilization and the pervasiveness of programming mistakes in popular media, emphasizing the importance of understanding these events.', 'chapters': [{'end': 7282.912, 'start': 7083.223, 'title': 'Integer overflow and binary arithmetic', 'summary': 'Discusses integer overflow and binary arithmetic, illustrating how adding 1 to the maximum value of integers can cause overflow, leading to unexpected results, and explaining how binary arithmetic works and the implications of limited memory in hardware.', 'duration': 199.689, 'highlights': ['Integer overflow occurs when adding 1 to the maximum value of integers, resulting in overflow and unexpected results, such as in the case of adding 1 to 999 in decimal or 7 in binary.', 'The concept of carrying over when adding 1 to the maximum value is explained, showcasing how carrying over occurs in decimal and binary arithmetic.', 'The implications of limited memory in hardware, such as using 32 or 64 bits to represent integers, are discussed, leading to potential integer overflow due to finite memory space.']}, {'end': 7790.442, 'start': 7283.292, 'title': '32-bit integer overflow', 'summary': 'Discusses the limitations of 32-bit integers in computers, as evidenced by a game capping its highest score at 4 billion and real-world consequences such as the y2k bug and a boeing 787 grounding due to integer overflow.', 'duration': 507.15, 'highlights': ['The maximum score in a game is capped at 4 billion due to the limitations of 32-bit integers, as 32 bits can represent numbers up to roughly 4 billion.', 'The Y2K problem is explained, where the use of two digits to represent years led to potential errors, as 1999 could overflow to 1900, causing widespread concerns and real-world consequences.', 'A Boeing 787 was grounded due to a programming error caused by a 32-bit integer overflow, where a software counter internal to the generator would overflow after 248 days of continuous power, leading to potential loss of electrical power.']}, {'end': 7993.918, 'start': 7790.743, 'title': 'Game of civilization and programming bugs', 'summary': 'Discusses how a programming bug in the game civilization made gandhi aggressively loop back to 255 due to integer underflow, and highlights the omnipresence of programming mistakes in popular media, bugs, hacks, and exploits, emphasizing the importance of understanding why and how such events occur.', 'duration': 203.175, 'highlights': ["The game Civilization had a programming bug where Gandhi's aggression level looped back to 255 due to integer underflow when he adopted democracy, making him as aggressive as possible.", "Programming bugs are omnipresent in popular media, bugs, hacks, and exploits, often caused by a programmer's mistake in code or failure to anticipate scenarios, leading to real-world consequences.", 'The chapter emphasizes the importance of understanding why and how programming mistakes occur and the need to recreate snippets of games from the past, translating childhood experiences into actual code.']}], 'duration': 910.695, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/ix5jPkxsr7M/pics/ix5jPkxsr7M7083223.jpg', 'highlights': ['A Boeing 787 was grounded due to a 32-bit integer overflow after 248 days of continuous power.', 'The Y2K problem caused widespread concerns due to potential 32-bit integer overflow.', 'Integer overflow occurs when adding 1 to the maximum value, leading to unexpected results.', "The game Civilization had a programming bug where Gandhi's aggression level looped back to 255.", 'The maximum score in a game is capped at 4 billion due to limitations of 32-bit integers.', 'Programming bugs in popular media often lead to real-world consequences.', 'Implications of limited memory in hardware can lead to potential integer overflow.']}], 'highlights': ['The chapter discusses the fundamental concepts of looping in C programming, emphasizing the use of variables, conventions for naming variables, and the rationale for starting counting from 0 rather than 1 in computers.', 'The chapter introduces the CS50 Sandbox, a cloud-based tool for coding, and explains the formatting of strings in C using printf.', 'The make command automates the compilation process and saves time by looking for a default file, hello.c, and automating the necessary steps.', 'The chapter introduces the possibilities in C programming, including different data types such as integers, characters, floats, and doubles, along with formatting options in printf.', 'The chapter explains the concept of functions in C, emphasizing their ability to take inputs, called arguments or parameters, and return values.', 'The importance of function declaration order in C programming is highlighted, emphasizing the significance of teaching the computer what a function is before using it.', 'A Boeing 787 was grounded due to a 32-bit integer overflow after 248 days of continuous power.', 'The Y2K problem caused widespread concerns due to potential 32-bit integer overflow.', 'Integer overflow occurs when adding 1 to the maximum value, leading to unexpected results.', "The game Civilization had a programming bug where Gandhi's aggression level looped back to 255."]}