Comments in C

Comments in C

Comments can be used to explain code, and to make it more readable. It can also be used to prevent execution when testing alternative code.

Comments can be singled-lined or multi-lined.

Single-line Comments

Single-line comments start with two forward slashes (//).

Any text between // and the end of the line is ignored by the compiler (will not be executed).

This example uses a single-line comment before a line of code:

Example

// This is a comment

printf("Hello World!");

This example uses a single-line comment at the end of a line of code:

Example

printf("Hello World!"); // This is a comment

C Multi-line Comments

Multi-line comments start with /* and ends with */.

Any text between /* and */ will be ignored by the compiler:

Example

/* The code below will print the words Hello World!

to the screen, and it is amazing */

printf("Hello World!");

Single or multi-line comments?

It is up to you which you want to use. Normally, we use // for short comments, and /* */ for longer.

Good to know: Before version C99 (released in 1999), you could only use multi-line comments in C.