[Boatanchors] IBM Selectric Terminal

[Michael D. Harmon]

A Selectric typewriter doesn't have the interface electronics to allow 
the keyboard and type mechanisms to be connected to an external data 
bus.   It's an electromechanical device.  When the System/360 computer 
systems were developed by IBM in the late Sixties, the operator console 
was a specialized Selectric mechanism designated the IBM 1052 
printer/keyboard.  I've spent thousands of hours in front of the old 
1052's.   IBM also had a variation of the 1052 which contained a printer 
only, called the 1053.  There were a number of variations of these 
devices customized for unique purposes, as well as a large variety of 
type elements ("balls"), ranging from many international languages to 
specialized character sets such as OCR fonts and the symbol set used by 
weather agencies.

It's been mentioned that the IBM System/360 architecture used EBCDIC 
(Extended Binary Coded Decimal Interchange Code), rather than ASCII.  
The EBCDIC code allowed 255 bit combinations per byte from 00 to FF 
hex.  Since the EBCDIC alphabet has twice the characters as the ASCII 
alphabet, some sort of translate table is needed to create the 
appropriate bit patterns when used in an ASCII environment.  For 
example, the lower case letters "a - z" in ASCII are 61 - 7A hex in a 
continuous sequence; in EBCDIC, they are 81-89 hex, 91-99 hex, and A2-A9 
with interspersed machine control characters.

As you can see, adapting an EBCDIC device for use in an ASCII 
environment is probably not worth anyone's time.  I've written assembler 
language code to do it, but you have to be a real glutton for 
punishment!  Adapting a Selectric office typewriter would be even more 
of a challenge.

Mike Harmon, WB0LDJ
Retired Mainframe Systems Programmer/Hardware Hacker
mharmon at att.net