We have learned about the following topics so far:

• Variables and Constants
• Data Types
• Keywords
• Input and Output in C programming

To understand these topics better, lets discuss first C program examples.

Program to Display "Hello, World!"

#include <stdio.h>
int main()
{
 printf("Hello,World");  //single line comment
 return 0;
/*
    multi
    line
    comments
/*
}

Output

Hello, World!

How "Hello, World!" program works?

• The #include <stdio.h> is a preprocessor command. This command tells compiler to include the contents of stdio.h (standard input and output) file in the program.

  The stdio.h file contains functions such as scanf() and print() to take input and display output respectively.

  If you use printf() function without writing #include <stdio.h>, the program will not be compiled.

• The execution of a C program starts from the main() function.
• The printf() is a library function to send formatted output to the screen. In this program, the printf() displays Hello, World! text on the screen.
• The return 0; statement is the "Exit status" of the program. In simple terms, program ends with this statement.