TRACE - display commands and statements before execution.

$*$TraCe $*$TraCe ON: traces statements by displaying them before execution; this is handy for debugging. $*$TraCe displays all statements, system commands and EXEC directives. $*$CoPy only displays system commands.
If you turn on tracing when $*$TraCe is already on, EXEC goes to an increased level of tracing. EXEC displays messages whenever it opens or closes a file, and on the execution or return of a user-defined command. It also prints out what a particular command line matches (whether this is an EXEC directive, system command, or user-defined command).
$*$TraCe OFF: turns off all tracing. If you have turned on $*$TraCe twice to get the increased level of tracing, a single $*$TraCe OFF turns off both levels of tracing. When EXEC begins execution, tracing is turned off.