multi line comment in arduino programming have the following syntax code example

Example: how to comment in arduino

x = 5;  // This is a single line comment. Anything after the slashes is a comment 
         // to the end of the line

/* this is multiline comment - use it to comment out whole blocks of code

if (gwb == 0){   // single line comments are OK inside a multiline comment
x = 3;           /* but not other multiline comments - this is invalid */
}
// don't forget the "closing" comment - they have to be balanced!
*/