Rational Developer for System z
PL/I for Windows, Version 8.0, Programming Guide

Suppress command display (@)

Syntax: @ command

The /S option globally suppresses the display of commands while NMAKE is running. The at sign (@) modifier suppresses the display for individual commands.

Regardless of the /S option or the @ modifier, output generated by the command itself always appears.

See Suppress command display (/S).

Rational Developer for System z
PL/I for Windows, Version 8.0, Programming Guide