AT&T 6300 Programmer's Manual page 469

Remarks
STRIG
Statement and Function
4 Returns -1 if button A2 was pressed since the last
STRIG(4) function call, returns 0 if not.
5 Returns -1 if button A2 is currently pressed, returns 0 if
not.
6 Returns -1 if button B2 was pressed since the last
STRIG(6) function call, returns 0
if
not.
7 Returns -1 if button B2 is currently pressed, returns 0 if
not.
STRIG ON must be executed before any
STRIG(n) function calls may be made. After
STRIG ON, every time the program starts a
new statement BASIC checks to see if a button
has been pressed.
If STRIQ is OFF, no testing takes place.
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