multi-line comment

Comments are lines in the program that are used to inform yourself or others about the way the program works. They are ignored by the compiler, and not exported to the processor Comments only purpose are to help you understand (or remember) how your program works or to inform others how your program works. There are two different ways of marking a line as a comment: single line comment and multi-line comments.
/* this is multiline comment - use it to comment out whole blocks of code

if (gwb == 0) {
    x = 3 
} // single line comment is OK inside a multiline comment
/* but not another multiline comment - this is invalid */

// don't forget the "closing" comment - they have to be balanced!

When experimenting with code, "commenting out" parts of your program is a convenient way to remove lines that may be buggy. This leaves the lines in the code, but turns them into comments, so the compiler just ignores them. This can be especially useful when trying to locate a problem, or when a program refuses to compile and the compiler error is cryptic or unhelpful.