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tion of his computer. The drawing is among the oldest preserved
sketches of a microcomputer designed for the consumer market.
The name “Key-Cassette” most likely derives from “Key-Edit.”
The drawing depicts a case in the style of a typical desktop cal-
culator of that time. The lower part of the front panel houses a
built-in keyboard. The top part contains a cassette drive on the
right, and either an acoustic coupler or a second cassette drive
on the left. A small display and some switches are placed in the
middle of the panel.
The annotated drawing provides enough information to let
us grasp the basic operations of the Key-Cassette. The small
thirty-two-key keyboard of the Key-Cassette would allow the
user to enter all the alphanumeric and numeric characters as
well as the APL and special function symbols. To achieve such
compactness, each key was designed to enter up to five symbols
(using a combination of keystrokes). The symbols on the keys
would be colour-coded to distinguish between symbols that
could be entered directly (red marks in the center of the keys)
and those that could be entered via a combination of keystrokes
(black marks placed in the corners of the keys).
The one-line display of the Key-Cassette would allow the user
to view a single line of APL code, a computer output, or an error
message. The rotate keys “
” would allow moving the
displayed information left and right to reveal it fully, and the
roll keys “
” and “
” would allow scrolling through the lines
of APL code. The sketch of the Key-Cassette is augmented with
two drawings of possible segmented display elements, one com-
prised of thirteen display segments and the other of fifteen seg-
ments. Finally, the tape cassette drives were to provide external
storage.
But that was early in 1972. The production model of the
MCM /70 developed two years later shared a number of features
with the Key-Cassette concept: the one-line display, the built-in
” and “
 
 
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