CS50x 02. C

This is the summary of CS50x course.

Intro

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• Recall that machines only understand binary. Where humans write source code, a list of instructions for the computer that is human readable, machines only understand what we can now call machine code. This machine code is a pattern of ones and zeros that produces a desired effect.
• It turns out that we can convert source code into machine code using a very special piece of software called a compiler.

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Visual Studio Code for CS50

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• You can open VS Code at cs50.dev

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Hello World

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• We will be using three commands to write, compile, and run our first program:
  • code hello.c creates a file and aloows us to type instuctions for this program.
  • make hello compiles the file from our instructions in C and creates an executable file called hello.
  • ./hello runs the program called hello
• We can build your first program in C by typing code hello.c into the terminal window.

// A program that says hello to the world

#include <stdio.h>

int main(void)
{
	printf("hello, world\n");
}

• printf is a function that can output a line of text.
• Notice that the \n creates a new line after the words hello, world.
• make is a compiler that will look for our hello.c fine and turn it into a program called hello.
• Now, type ./hello and your program will execute saying hello, world.
• You will notice that there is now both a file called hello.c and hello.
  • hello.c is able to be read by the compiler: It’s where your code is stored.
  • hello is an executable file that you can run but cannot be read by the compiler.
• \ character is called an escape character that tells the compiler that \n is a special instruction to create a line break. There are other escape characters you can use:

\n    create a new line
\r    return to the start of a line
\"    print a double quote
\'    print a single quote
\\    print a backslash

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