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C Comments


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!");
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This example uses a single-line comment at the end of a line of code:

Example

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


C Exercises

Test Yourself With Exercises

Exercise:

Comments in C are written with special characters. Insert the missing parts:

 This is a single-line comment
 This is a multi-line comment 
 

Start the Exercise