Using the CNTRL Macro to Control an I/O Device

The CNTRL macro performs these device-dependent control functions:

Card reader stacker selection (SS)
Printer line spacing (SP)
Printer carriage control (SK)
Magnetic tape backspace (BSR) over a specified number of blocks
Magnetic tape backspace (BSM) past a tape mark and forward space over the tape mark
Magnetic tape forward space (FSR) over a specified number of blocks
Magnetic tape forward space (FSM) past a tape mark and a backspace over the tape mark

Backspacing moves the tape toward the load point; forward spacing moves the tape away from the load point.

Restriction: The CNTRL macro cannot be used with an input data set containing variable-length records on the card reader.

If you specify OPTCD=H in the DCB parameter field of the DD statement, you can use the CNTRL macro to position VSE tapes even if they contain embedded checkpoint records. The CNTRL macro cannot be used to backspace VSE 7-track tapes that are written in data convert mode and contain embedded checkpoint records.