CS50x 2024 - Lecture 2 - Arrays 

I love how David first shows us how things are done in the old-school way as well as the logic behind it, then slams those teachings in by revealing some sort of library that makes our lives 10 times easier 😆

The best university in the world still doesn't have air conditioning to cool David. I'm sweating watching it.

i have 5+ years of dev experience + 5 additional years in uni , but still this is good to see

I liked the detail about 72, 73, 33 used earlier without context and then having them as result changing variables from chars to integers and getting 'HI!' :)

talking out loud to an inanimate object is such great advice, i remember when i was young how often i would ask my parents stuff and as soon as i said it the answer was clear as day lol

I do really love the fact even if he is a teacher and a great programmer, he make mistake aswell. That make me more confident than even after years and years of programming you going to always make mistake even the basic one and you don't need to feel you are bad at programming.

This course is killing all paid courses so far) Excited to see what's next!

best lecture so far this was so fun

What an amazing teacher

The video covers the use of integers to calculate averages, the importance of using floats for accurate division, and the introduction to arrays in C programming. It also discusses the compiling process, debugging techniques, and the representation of strings as arrays of characters in computer memory. The importance of exit status codes, cryptography, and encryption concepts are also explained. 00:00 Exploring Reading Levels and Compiling Code 01:03CS50 week 2 begins with a story time activity to explore reading levels and writing code. 01:27Volunteers read different stories to determine the reading levels and discuss the characteristics of the text. 07:05The video transitions to discussing compiling code and the role of the make command in running a compiler. 08:49 Understanding Clang and Compiling Source Code 08:49Clang converts source code to machine code, but lacks user-friendliness. 09:16Clang defaults to naming output file 'a.out', which is not user-friendly. 14:59Compiling involves pre-processing, compiling, assembling, and linking. 17:41 Understanding the Compiling Process in C Programming 17:44The prototype for get_string is defined inside cs50.h. 19:30Preprocessing, compiling, assembling, and linking are the four steps in the compiling process. 24:22Compiling converts C code into assembly language, which is then converted to 0's and 1's in the assembling step. 26:27 Implications of Source Code to Machine Code and Debugging Techniques 26:31Compiling code implies potential for decompiling it, reversing 0's and 1's to source code. 27:11Reverse engineering machine code back to source code is challenging due to loss of variable and function names. 32:53Debugging techniques like using printf and helper functions are essential for identifying and fixing bugs in code. 35:17 Debugging with a Debugger: A Step-by-Step Guide 35:17Using a debugger to step through code line by line and understand its execution. 41:47Setting breakpoints to pause execution at specific lines of code and inspect variables. 42:54Stepping into functions to understand their internal execution and inspect variable values. 44:10 Debugging Techniques and Memory Representation in C 44:10Using debuggers like debug50 and VS Code's debugger can help visualize code execution step by step. 45:52Rubber duck debugging involves explaining code out loud to an inanimate object to identify logical errors. 51:53Memory in computers is represented as a canvas of bytes, and different data types occupy different amounts of memory. 53:03 Understanding Arrays and Memory in C Programming 53:03Using integers to calculate average of scores. 53:27The importance of using floats instead of integers for accurate division. 57:46Introduction to arrays and their syntax in C programming. 1:01:52 Improving Code Design and Working with Arrays 1:01:52Clearing the terminal and making scores again. 1:02:38Using a loop to improve code design and avoid repetition. 1:03:11Explaining the use of arrays and their indexing in C programming. 1:09:36Addressing the issue of calculating the length of an array in C. 1:10:43 Understanding Arrays and Strings in C 1:10:43Average function iterates over an array, adds up numbers, and divides by total number of numbers. 1:11:10Declaring a variable called scores of size n and iterating through the array. 1:18:35Exploring the concept of strings as arrays of characters in C. 1:19:34 Understanding Strings and Memory Representation 1:19:37Strings in C are represented as arrays of characters, and the computer uses a special sentinel value to indicate the end of a string. 1:21:07The sentinel value at the end of every string in a computer's memory is all 0 bits, indicating the end of the string. 1:23:48In C, strings are represented as arrays of characters, and the NUL value is used to terminate strings, ensuring proper memory representation. 1:28:23 Understanding Strings and Arrays in C 1:28:24A string is an array of characters. 1:29:54Arrays in C are zero-indexed and can be manipulated using loops. 1:33:30Demonstration of finding the length of a string and modularizing it into a function. 1:37:10 Exploring C Libraries and Header Files 1:37:10Understanding local variable scope in C 1:37:43Exploring the string.h library and strlen function 1:41:54Optimizing code efficiency by avoiding redundant function calls 1:44:58Using conditional statements to convert lowercase characters to uppercase 1:45:59 Using Command Line Arguments in C Programming 1:46:03Explaining how to print a character without a new line and force it to uppercase 1:46:21Leveraging ASCII chart to convert lowercase to uppercase without using CS50 1:50:06Introduction to using command line arguments in C programming 1:54:50 Understanding Command Line Arguments and Exit Statuses in C Programming 1:54:57Command line arguments allow for user input when running a program 2:00:08Exit statuses are special return values from a program, with 0 indicating success 1:56:31Using conditional statements, error checking can be implemented based on command line arguments 2:03:43 Understanding Exit Status Codes and Introduction to Cryptography 2:03:43Understanding exit status codes in C programming and the significance of return values. 2:05:58Introduction to cryptography, encryption, and the concept of plaintext and ciphertext. 2:07:15Explanation of simple ciphers like the Caesar cipher and the concept of keys in encryption.

Currently retired and with 40 yrs tech exp but have been enjoying this. Moving on to 3rd session

2:09:30 In case it isn't obvious, the nice thing about rot13 is that decryption is the same as encryption. You're adding 13 either way.

Just finished , learnt so much in this.

this course pretty cool I just started coding about a 2 month ago I pretty much know most of this stuff so far but I wanted to go thru all the exercises for any extra practice and info I might missed

oh my goodness,this is the best course i ever taken!and the outro is so expressive!really thanks,david!

Thank you, David

This is my intro to coding, and I couldn't be happier (:

Mr. Malan is a fantastic presenter

Awesome stuff!

This is fantastic.

pure gold. of to the next one. after pset 2

1:42:34 Actually, in C, the condition of a loop is evaluated before each iteration. So, if we assign a function to a variable and use that variable as the condition inside the loop, the function will be called each time the loop condition is evaluated, not just once

1st lecture was pure fun , but lecture 2 was hard.

Thanks ❤❤

This is very usefull content.

Amazing 👉🏽✨✨✨

this is good i cant be bothered to learn c on my own but this is entertaining so im watching it

35:50 JAJAJAJAJAJAJ. I might look simple and stupid but this little details make the learning process better

So good

Respect

1:23:00 But in JavaScript if we create a string and the trynna access it like an array like: name[0], we can't access anything after the last character??

Thabk you

I have been using rubber duck debugging without knowing about it, I talk to myself what is program is doing and believe me it's really helpful XD.

Imagine going on stage for cookies and getting a book instead.

1:35:11 if you start counting with 0, why does it output that David = 5? isnt the last d at index position 4? and its not counting \0 so isnt the answer 4?

On the example starting at 1:10:00, is “length” not supposed to be assigned a value?

كورس فخم

So anyone know what lightbulbs had encrypted in them? I don't think I can see the binary from the video.

the quality of content is just next lvl .

You can calculate the length of an array on the stack: #define ArraySize(X) ((int)(sizeof(X)/sizeof(X[0]))) The speaker was probably mistaken with a heap array.

Why does the cs50 and stdio are saved in .c, why didn't it save in binary? In that way they could skip the first 3 steps, and just be linked to your code

Yeahhhhhhh 🎉🎉🎉🎉🎉🎉

It feels we will grow older with Mr. David Malan

lecture 2, gl to everyone

Can anyone tell me how to solve the undefined reference to get_string? I have downloaded the cs50 library but stll can't fix the error

i have a question if CS50.h is stored somewhere else as cs50.c then if i save some other file in the same name will it not confuse with that file?

where is the value of int length declared? 1:13:20 argc == 2? didn't get. 1:56:12

guys can anyone tell me is that same with 2023 one, because I have begun already in edX?

David J Malan is perfect person

Personal Bookmark 48:00

I don’t remember void meow(void). What does that do?

2024 🎉

C doesn’t have a string type by default, it is implemented in the cs50.h file right?

We also want some snacks here!

1:13:52 - i wish i could have those snacks too :( but dont worry! see you in ten!

Get this man a towel

❤❤❤

just went outside no rubber duck was there false advertising

Can anyone help me with codespace restart

35:56 that made me laugh so hard lol

I just got back to these because it's amazing the amount of things that can happen in just two months and I cannot, for the life of me remember how it was that I was able to do everything in the command line using only vim, node and virtual environments xD And I really do not feel like learning all over again as I remember it took quite the amount of time and I had to install Arch Linux, also lost all of my music files because this laptop is obscenely small and weak. Should have got myself something better when I had the chance

What book did the third kid get?

Wow

1:19:00

1:14:08

i just noticed i had a duck on my desk all along, literally.... just didnt think it was meaningful when i first saw the duck in the course`s cover

1:50:00

47:00

Intro music feels like a cult movie 😂

He literally gave her a Dr. Seuss book 😂🤣

48:01

Thanks for all the material, this is great! However I would refrain from using cs50.h as a library as it hides C's real code and its not a standard library. It quickly becomes useless when one is back at home with just C.

I want a rubber duck too :(

please do intermittent fasting for our longevity，mr. professor.

isnt it ironic that the AMERICAN ASCII chart's first value is Zero in German (Null) and not in English? xD

can i get a duck to?

1like = 5pushups in 2024

Programming Languages Such as Java, C#, C/C++ and Visual Basic/Pascal are Different but Also Similar. They All Have: Branching (If Statements to Run some Code and Not Some Other Code) Looping: For and While Loops - To Repetitivly Run the Same Code. Variables and Arrays - To Hold Data for Processing. Functions and Procedures: Blocks of Code to Run Multiple Times. How to Learn Programming: You Have to Learn the Language. Such as Java, or C#. Learn the Syntax: How you Declare and Use Variables or Arrays. What is the Syntax for Branching If Statements. Then YOU Need to use Your Brain. You Need to Think. HOW Can I Use Variables, Branching, Loops and Functions to Write Tic / Tac /Toe. Then Use your Brain to Write Pong. Then Use Your Brain to Write Tetris. Programming is NOT Merely: Finding the Solution (Copying from someone else) Tic / Tac /Toe , Pong and Tetris. YOU'RE P1G BRAIN IS UNABLE TO DO THAT. ALL YOU CAN DO IS, FIND THE SOLUTION FOR TIC/TAC/TOE FROM SOMEONE ELSE. MEMORISE AND REPEAT THAT. THEN YOU GET THE SOLUTION FOR PONG FROM SOMEONE ELSE. MEMORISE AND REPEAT THAT. THEN YOU GET THE SOLUTION FOR TETRIS FROM SOMEONE ELSE. MEMORISE AND REPEAT THAT. Then YOU Need to use Your Brain. You Need to Think. HOW Can I Use Variables, Branching, Loops and Functions to Write Tic / Tac /Toe. Then Use your Brain to Write Pong. Then Use Your Brain to Write Tetris. Programming is NOT Merely: Finding the Solution (Copying from someone else) Tic / Tac /Toe, Pong AND Tetris. YOU'RE P1G BRAIN IS UNABLE TO DO THAT. ALL YOU CAN DO IS, FIND THE SOLUTION FOR TIC/TAC/TOE FROM SOMEONE ELSE. MEMORISE AND REPEAT THAT. There Isn't One Solution or Answer for a Programming Exercise Such as Tic / Tac /Toe or Pong. They Can be Written in Several / Multiple. SEVERAL / MULTIPLE CORRECT / RIGHT ANSWERS.

Trace the program how we getting output

37:43