IBM Personal Computer AT Manual To Operations page 42

Pause stops your program.
Press and hold the Ctrl key. Then, press the Num Lock
key to generate a pause. Press any key to continue.
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Clear Screen removes all information from the screen
and moves the cursor to the upper-left corner.
Press and hold the Ctrl key. Then, press the Home key
~
to generate a clear screen.
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1-18 Keyboard