IBM Professional Series User Manual page 374

The 370 Program Status Register is always displayed on the
screen and you may edit it when the processor is in the
"STOPPED" state. If the processor is not stopped, the field
is locked.
Note that the 370 Instruction Counter, the 370 Condition
Code, and the CMWP fields are taken from the PSW and
displayed immediately below the 370 Program Status Word
Register. You may not change these fields.
If
you want to
change them, you change the PSW.
F3 Key - Edit (GPRjFPRjCR)
You can edit the 370 GENERAL PURPOSE REGISTERS if
they are displayed on the screen and the fields are unlocked.
Again, the fields are unlocked if the processor is stopped.
If you want to edit the 370 FLOATING POINT
REGISTERS or the CONTROL REGISTERS, they must be
displayed on the screen. Press the F3 key to display them.
When you press the F3 key the register display area of the
screen is overlayed with a different set of registers. Initially,
the 370 General Purpose Registers are displayed in this area.
If
you press F3, the Floating Point registers are displayed.
Press F3 again and the Control Registers are displayed.
Press F3 again and the General Purpose registers are again
displayed. You can move through displays of these 3 sets of
registers by pressing the F3 key.
Storage Edit
The storage display area of the screen initially displays the
370 real main storage. Sixteen bytes of storage are displayed
on thirteen consecutive lines. The six digit addresses are
displayed on the left side of the screen, followed by the
storage contents. The fields are unlocked so you may edit
them if the processor is stopped.
You can specify the starting address of the storage display by
typing an address in the storage edit address field. Note that
this field is located where the first storage address is
displayed on the screen. (See Figure B-1 on page B-2.) It is
the only address that isn't highlighted, and the cursor is
generally placed at the beginning of this field. You need not
Appendix B. The 370 Processor Control Session B-5