AT&T 6300 Programmer's Manual page 27

Getting Started
CTRL-ALT-DEL
Performs a System Reset by holding down the CTRL and
ALT keys, and then pressing DEL.
CTRL-PRTSC
All text sent to the screen is also sent to the system printer.
A second CTRL-PRTSC will stop printing. If you press
PRTSC while holding down SHIFT, MS-DOS will make a
single printed copy of the entire display screen.
CTRL-L
Outputs a formfeed character.
It
has the same function as
the CLS statement, (Le., it clears the screen or the current
graphics viewport, if a viewport has been defined).
CTRL-Z
Sets an end of file condition (see the "OPEN COM State-
ment" in the Reference section).
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