[GreenKeys] [External] Re: Teletype DRPE tuned reed mechanism

[Jones, Douglas W]

From: Eric Moore [mooreericnyc at gmail.com] -- Monday, December 28, 2020 9:32 AM

> Do you happen to know what device was used for punching 8 level paper tape prior to 1954?

I don't thik 8-level tape was used by anyone back then.  All the 1950s computers used 6-level codes.  Word sizes were multiples of 6 bits, with 36 bit words being dominant for large computers, with small computers being made in 12, 18 and 24 bit words.

The DEC PDP-8 from 1965 was the first computer DEC made where ASCII was the standard code used internally and the Model 33 ASR tty as the default console I/O device.  All earlier DEC machines used 6-bit character sets, and they used Flexowriters for console devices.

IBM's System 360, also 1965, was their first machine with 32-bit words and an 8-bit byte (except some research machines).  They developed EBCDIC, and 8-bit character code, for that machine.  All their earlier offerings used BCD, a 6-bit character code.  Both EBCDIC and BCD were encodings of the 12-bit Hollerith code on punched cards.  The logic to compress 12 bits to 6 or 8 bits was trivial and directly explains the odd gaps in the assignment of BCD and EBCDIC codes.

The LGP-30 computer, one of the best selling very small computers, introduced in 1957, used a 6-bit code on its Flexowriters.

ASCII was developed by Teletype Corp (with strong input from the computer industry) in 1964.  It was, of course, a natural extension of Teletype corp's 5-level Baudot code.  The Flexowriter Programmatic line also used 8-level tape; I think the Flexowriter SPD was the first of their machines to go 8-level.

       Doug Jones
       jones at cs.uiowa.edu