IBM 5155 Manual To Operations page 199

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When pressed, the Spacebar moves the cursor to the
right. Any character the cursor moves over is replaced
with a blank.
[1.8]J
The Alternate key, when pressed with any alphabetic
key, provides an easy way of entering BASIC
keywords. Press the Alt key and an alphabetic key, and
the BASIC keyword is entered. ASCII codes also can
be entered with the Alt key and the numeric keypad.
For more information about the Alt key, see the BASIC
Reference manual, part number 6025010.
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The Control key performs a variety of functions. These
are defined in your operating system manual or
application program manual.
Keyboard 3-11