More information from Tim Coslet of the Computer History Museum 1620 Team: The Model I printed a Cyrillic Ж for invalid character codes. The width of the Cyrillic Ж was narrower than shown at left, so that it matched the width of other characters the typewriter typed. The Model II printed a character called "pillow" for invalid character codes. "Pillow" was a solid black rectangle.
Ken Shirriff (the other Ken) On Wed, Sep 27, 2017 at 1:36 PM, Ken Shirriff <ken.shirr...@gmail.com> wrote: > I checked with the Computer History Museum about the 1620. According to Dave > Babcock, IBM 1620 Restoration Team Lead at the CHM: > > The 1620 console typewriter actually had a "zha" character typebar that > it would use for unknown characters. > > The only overprinting that the typewriter would do was a "flag" mark [an > "overscore" rather than an "underscore"] and a center-hyphen [used for > characters with bad parity]. For both of these, it would first print > the special character [flag or center-hyphen] without advancing the > carriage, then print the other digit or alpha character. > > And yes, it was possible to get a "bad parity unknown character" which > would print the center-hyphen and zha. > > The typewriter was not capable of backspacing to do any other overprinting. > > With the Wheelwriter-based console typewriter that we're using for the > IBM 1620 Jr. we will be doing some real print-backspace-print > overprinting to approximate some of the special characters, like zha. > > Ken Shirriff (the other Ken) > > On Mon, Sep 25, 2017 at 9:48 PM, Leo Broukhis via Unicode < > unicode@unicode.org> wrote: > >> Wikipedia (https://en.wikipedia.org/wiki/IBM_1620#Invalid_character) >> describes the "invalid character" symbol (see attachment) as a Cyrillic Ж >> which it obviously is not. >> >> But what is it? Does it deserve encoding, or is it a glyph variation of >> an existing codepoint? >> >> The question is somewhat prompted by >> >> 2BFF 1 HELLSCHREIBER PAUSE SYMBOL >> >> in the pipeline, although I learned about both earlier today within a few >> minutes of one another. >> >> Thanks, >> Leo >> >> >
