HP 3000 Manuals

HP C/iX Reference Manual

Comments 

You can include comments to explain code in your program by enclosing the
text with /* and */ characters.  If the /* character sequence is located
within a string literal or a character constant, the compiler processes
them as "normal" characters and not as the start of a comment.

You cannot nest comments.  To comment blocks of code, enclose the block
within the #if and #endif statements, as shown below:

     #if 0
         .
         .
        code
         .
         .
     #endif

MPE/iX 5.0 Documentation