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 is a comment  
printf("Hello World!");
 
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:

/* The code below will print the words Hello World!  
to the screen, and it is amazing */  
printf("Hello World!");