HP 2641A APL Display Station

HP 2641A terminal, connected to HP 3000 Series II system, running
APL\3000 software system.


Probably September 1976


The 2641A is essentially a 2645A with an additional firmware card and a
few replaced ROM chips and the additional character set ROMs with the
APL character set


The 2641A keyboard is almost identical to that of the 2645A except that
the Memory Lock button and its red LED indicator have been changed to
toggle in and out of "APL Mode" (which can be done programmatically by
sending ESC> to enter APL Mode or ESC< to return to non-APL mode). In
non-APL mode the terminal is essentially identical in features and
behavior to the 2645A. In APL mode, unshifted character entry gives
upper-case characters and shifted characters give the special APL
characters. Also in APL mode, the terminal supports simulation of
character overstrikes to produce composite APL characters (of a limited
set that have glyphs in the character set) So for example if the user
types a character, then hits backspace, then enters a second character,
the terminal will replace that triplet with a single APL overstrike
character if it has a mapping/glyph for that pair of characters
superimposed (for example the APL "domino" character which consists of
the APL QUAD (box) character with a traditional division sign
overstruck). It will perform the same translation bidirectionally when
communicating with the host, so if you transmit the combined character
to the host it will get expanded back into the three character sequence.
The same mechanism supports APL-style underlined letters as well.