18-bit computing: Difference between revisions

Revision as of 15:04, 30 December 2013

Revision as of 23:55, 18 June 2015

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* The [[BCL Molecular]]

* The NASA Standard Spacecraft Computer [[NSSC-1]]

== character encoding ==

18-bit machines use a variety of character encodings, including:

* [[DEC Radix-50]] (called Radix 50₈ format) packs three characters plus 2 bits in each 18-bit word.<ref>Digital Equipment Corporation, ''PDP-9 Utility Programs--Advanced Software System--Programmer's Reference Manual'', [http://www.bitsavers.org/pdf/dec/pdp9/DEC-9A-GUAB-D_UTILITIES.pdf full text], Digital Equipment Corporation, 1968, Appendix 1.</ref>

* "Teletype" packs 3 characters in each 18-bit word; each character a 5-bit [[Baudot code]] and a upper-case bit.<ref name="pdp7" />

* [[DEC SIXBIT]] (often called "ASCII") packs 3 characters in each 18-bit word,<ref name="pdp7">

[http://bitsavers.trailing-edge.com/pdf/dec/pdp7/PDP-7_AsmMan.pdf "PDP-7 Symbolic Assembler Programming Manual"].

p. 6; p. 38-39.

</ref> each 6-bit character obtained by stripping the high bits from the 7-bit ASCII code, which folds lowercase to uppercase letters.

==References==

{{reflist}}

* [http://research.microsoft.com/Users/gbell/Digital/timeline/18-bit.htm DIGITAL Computing Timelime: 18-bit architecture]

* [http://simh.trailing-edge.com/docs/architecture18b.pdf ''Architectural Evolution in DEC’s 18b Computers''], Bob Supnik, 2006.