1.1. Program Structure

Before we study the basic building blocks of the C programming language, let us look at a bare minimum C program structure so that we can take it as a reference in the upcoming chapters.

1.1.1. Hello World Example

A C program basically consists of the following parts,

• Preprocessor Commands

• Functions

• Variables

• Statements & Expressions

• Comments

Let us look at a simple code that would print the words “Hello World”,

#include <stdio.h>

int main()
{
   /* my first program in C */
   printf("Hello, World!\n");
   
   return 0;
}

Let us take a look at the various parts of the above program,

• The first line of the program #include <stdio.h> is a preprocessor command, which tells a C compiler to include stdio.h file before going to actual compilation.

• The next line int main() is the main function where the program execution begins.

• The next line /*...*/ will be ignored by the compiler and it has been put to add additional comments in the program. So such lines are called comments in the program.

• The next line printf(...) is another function available in C which causes the message “Hello, World!” to be displayed on the screen.

• The next line return 0; terminates the main() function and returns the value 0.