A comment is a sequence of characters (on one or more lines) delimited by /* and */. Within these delimiters any characters are allowed. Comments can contain other comments, as long as each begins and ends with the necessary delimiters. They are called nested comments. Comments can be anywhere and can be of any length. They have no effect on the program, but they do act as separators. (Two tokens with only a comment in between are not treated as a single token.)

/* This is an example of a valid REXX comment */

Take special care when commenting out lines of code containing /* or */ as part of a literal string. Consider the following program segment:

01    parse pull input
02    if substr(input,1,5) = '/*123'
03      then call process
04    dept = substr(input,32,5)

To comment out lines 2 and 3, the following change would be incorrect:

01    parse pull input
02 /* if substr(input,1,5) = '/*123'
03      then call process
04 */ dept = substr(input,32,5)

You can avoid this type of problem by using concatenation for literal strings containing /* or */; line 2 would be:

if substr(input,1,5) = '/' || '*123'

You could comment out lines 2 and 3 correctly as follows:

01    parse pull input
02 /* if substr(input,1,5) = '/' || '*123'
03      then call process
04 */ dept = substr(input,32,5)