Comments are non-executable text used to document source code. Whitespace separates tokens and improves readability without generally affecting how C interprets the program.

#include <stdio.h>

int main()
{
    // Display a message
    printf("Hello\n");

    /*
       Display another message
       on the next line.
    */
    printf("C programming\n");

    return 0;
}

Example Output #

Hello
C programming

Explanation #

C provides two forms of comments.

A single-line comment begins with // and continues to the end of the line:

// Display a message

A block comment begins with /* and ends with */:

/*
   Display another message
   on the next line.
*/

Comments are ignored during translation and do not produce executable operations themselves.

Whitespace #

Whitespace includes spaces, tabs, and newlines. It is generally used to separate tokens and format source code.

These statements are equivalent:

int number = 10;

int
number
=
10
;

Whitespace can also be omitted where tokens remain unambiguous:

int number=10;

However, whitespace can be required to separate adjacent tokens. For example:

int number;

cannot be written as:

intnumber;

because intnumber is interpreted as a single identifier.

Comment and Whitespace Reference #

Comments and whitespace can improve source-code readability, but comments do not affect the runtime behavior of the program.