IBM 3151 Manual To Operations page 69

Keyboard Functions
KEY
Caps Lock
~
Clear
Control
Cursor Move
FUNCTION
Locks the keyboard in up-shift (for alphabetic keys only) mode.
Pressing this key again resets up-shift mode.
Erases all characters in the active page where the cursor is located,
and moves the cursor to the first position of the page.
Also clears the field attributes and the tab stops, and resets insert
mode.
Selects the function indicated on the front of the other selected keys.
Moves the cursor in the direction of the arrow.
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IB~ 31~1 Guide to Operations