IBM Professional Series User Manual page 302

preceded by a logical line end symbol
(#).
Any program
execution in progress is suspended until the Immediate
command is processed.
None of the Immediate commands issue responses.
HT: Use the HT command to suppress all terminal output
generated by any CMS command or your program that is
currently executing. The format of the HT command is:
Usage Notes:
1. Program execution continues. When the ready message
is displayed, normal terminal output resumes. Use the
R T command to restore typing or displaying.
2. CMS error messages having a suffix letter of S or T
cannot be suppressed.
HX: Use the HX command to stop the execution of any
CMS command or program, close any open files or I/O
devices, and return to the CMS command environment. The
format of the HX command is:
Usage Notes:
1. HX clears all file definitions made via the FILEDEF
command, including those entered with the PERM
option.
2. The HX command is executed when the next SVC or
I/O interruption occurs; therefore a delay may occur
between keying HX and the return to CMS. All terminal
output generated before HX is processed is displayed
before the command is executed.
3. HX does not clear user storage.
Chapter 7. VM/PC Commands 7-129