Comments are used to document an Open PL/I program. A comment can appear anywhere that a blank can appear and is equivalent to a blank. Comments cannot be nested. The general form of a comment is:
/*Comments open with a slash* and close with a *slash */
For example,
/*HERE IS A COMMENT*/ IF A<25 /* HERE IS ANOTHER ONE */ THEN /*HERE IS AN /* ERRONEOUS */ COMMENT */
The final comment is invalid because comments cannot be nested; it ends at the first * / in the line and the Compiler attempts to interpret COMMENT */ as code and produces an error message.
The Compiler puts an asterisk (*) into the line number field of the listing file for each line on which a comment is continued from a preceding line. This convention can be used to determine if some text was accidentally included in a comment.
Comments can continue over any number of lines of program text; thus, if the */ is omitted from a comment, all program text up to the next */ is considered part of the comment. This causes part of the program to be ignored by the Compiler and may cause it to produce misleading error messages. The same problem occurs if a character-string or bit-string constant is not terminated with an apostrophe.