Let’s start with a brief history of the C programming language.

The History of C

The C programming language was invented in the Bell Labs in 1969 as a by product of the UNIX operating system. It was developed by Dennis Ritchie and Ken Thompson as an easier way to code on the UNIX platform.

For further reading, read: History of C

King, K. N. (2008). C Programming: A Modern Approach (2nd ed.). New York, NY: W.W. Norton & Company.

C Fundamentals

Writing a simple program

/*	Program letus.c	*/

#include <stdio.h>

int main(void)
{
	printf("Let us C!\n");
	
	return 0;
}

Filename: letus.c

Every C program follow a general form

directives

int main(void)
{
	statements;
}

What are directives?

Before a C program is compiled, it is first edited by a program called a preprocessor. Commands intended for the preprocessor are called directives.

In the program letus.c, it begins with the line:

#include <stdio.h>

This is a directive to the preprocessor to include the information found in the header <stdio.h> in to the program letus.c before it is compiler. We will discuss headers more in-depth as we become more familiar with C.

<stdio.h> is the header responsible for Standard Input and Output within the program. It enables us to use the standard function printf() in our programs.

C has many headers like <stdio.h>; each contain information about some functionality provided by the standard library.

Note: The C Standard library is a set of pre-compiled functionality that enables us to do regular functions without having to reinvent the wheel.