C Introduction

C is a fast, simple and powerful programming language that has been in use for more than 50 years.

What is C?

• C was created by Dennis Ritchie at Bell Labs in 1972
• It was first used to write the Unix operating system
• C is a compiled language: your code is turned into a program the computer can run directly
• C is close to the hardware, so it gives you direct control over memory

Where is C Used?

How a C Program Runs

1. You write code in a file ending with .c, for example hello.c.
2. A compiler such as gcc checks the code and turns it into a program (an executable).
3. You run the executable.

gcc hello.c -o hello
./hello

On Windows the program is called hello.exe, and you run it with hello.

Setting Up

You need two things:

• A compiler: GCC. On Windows install it with MSYS2 or MinGW-w64; on Linux run sudo apt install gcc; on macOS install the Xcode command line tools
• An editor: Visual Studio Code with the C/C++ extension, or Code::Blocks, which comes with a compiler built in

Your First Program

Save this as hello.c:

#include <stdio.h>

int main(void) {
  printf("Assalam o Alaikum!\n");
  printf("This is my first C program.\n");
  return 0;
}

Assalam o Alaikum!
This is my first C program.

C Can Calculate

#include <stdio.h>

int main(void) {
  int rent = 25000;
  int months = 12;
  printf("Yearly rent: %d\n", rent * months);
  return 0;
}

Yearly rent: 300000

The %d inside the text is replaced by the number. You will learn more about this in the next chapter.

Exercise