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'''Sinclair ZX81''', (ZX81, Timex Sinclair 1000)<br/>
a low-cost [https://en.wikipedia.org/wiki/Home_computer home computer] developed by [[Sinclair|Sinclair Research]] and manufactured in [https://en.wikipedia.org/wiki/Scotland Scotland] by [https://en.wikipedia.org/wiki/Timex_Group_USA Timex Corporation], launched in the [https://en.wikipedia.org/wiki/United_Kingdom UK] in March 1981, and as slightly modified [https://en.wikipedia.org/wiki/Timex_Sinclair_1000 Timex Sinclair 1000] in the [https://en.wikipedia.org/wiki/United_States US] in July 1982. The ZX81 consists of a 3.5 MHz [[Z80|Z80A]] CPU from [https://en.wikipedia.org/wiki/NEC Nippon Electric Company], an [https://en.wikipedia.org/wiki/Application-specific_integrated_circuit ASIC] dubbed Sinclair Computer Logic, an 8 [https://en.wikipedia.org/wiki/Kibibyte KiB] [[Memory#ROM|ROM]] with the [https://en.wikipedia.org/wiki/Operating_system operating system], the [[Basic#Sinclair|Sinclair BASIC]] interpreter, and one KiB of [[Memory#RAM|RAM]], which could be expanded externally to 16 KiB. For I/O it had a [https://en.wikipedia.org/wiki/Membrane_keyboard membrane keyboard], a [https://en.wikipedia.org/wiki/RF_modulator RF modulator] to output 24 lines x 32 [https://en.wikipedia.org/wiki/Characters_per_line characters] or 64x48 [https://en.wikipedia.org/wiki/Pixel pixel] as [https://en.wikipedia.org/wiki/Signal_%28electrical_engineering%29 signal] for a [https://en.wikipedia.org/wiki/Television television], and a [https://en.wikipedia.org/wiki/Serial_port serial port] and [https://en.wikipedia.org/wiki/Softmodem softmodem] <ref>[http://www.wearmouth.demon.co.uk/zx81.htm Assembly Listing of the Operating System of the Sinclair ZX81] - THE 'SAVE COMMAND' ROUTINE, THE 'LOAD COMMAND' ROUTINE</ref>, to store and load [[Program|programs]] and [[Data|data]] to or from an external [https://en.wikipedia.org/wiki/Audio_cassette audio cassette] [https://en.wikipedia.org/wiki/Tape_recorder recorder] with 250 [https://en.wikipedia.org/wiki/Baud baud] <ref>[https://en.wikipedia.org/wiki/ZX81 ZX81 from Wikipedia]</ref>.
[https://en.wikipedia.org/wiki/Jim_Westwood Jim Westwood's] technical dodge using [https://en.wikipedia.org/wiki/Non-maskable_interrupt non-maskable interrupts] solved the flicker problem of the [https://en.wikipedia.org/wiki/ZX80 ZX80] and gave the ZX81 a "multi-tasking" SLOW mode with a steady display <ref>[http://www.wearmouth.demon.co.uk/zx81.htm Assembly Listing of the Operating System of the Sinclair ZX81] - THE 'NON MASKABLE INTERRUPT' ROUTINE</ref>, slowing down programs fourfold <ref>[https://en.wikipedia.org/wiki/ZX81 ZX81 from Wikipedia]</ref>. [[Z80]] [https://en.wikipedia.org/wiki/Machine_code machine code] could be inlined at absolute addresses and called via USR <ref>[http://yourcomputeronline.wordpress.com/tag/stuart-nicholls/page/3/ Stuart Nicholls] ('''1982'''). ''[http://yourcomputeronline.wordpress.com/2012/09/22/zx-81-games-writing/ ZX-81 Games Writing]''. [[Your Computer]], [http://yourcomputeronline.wordpress.com/2011/11/13/november-1982-contents-and-editorial/ November 1982]</ref> or encoded in [https://en.wikipedia.org/wiki/Comment_%28computer_programming%29#BASIC comment lines] <ref>[[David Horne]] ('''1982'''). ''[http://yourcomputeronline.wordpress.com/2012/10/21/chess-in-1k/ Chess in 1K]''. [[Your Computer]], [http://yourcomputeronline.wordpress.com/2012/10/04/december-1982-contents-and-editorial/ December 1982]</ref>, which could be executed after some appropriate [https://en.wikipedia.org/wiki/PEEK_and_POKE POKE] instructions.
=Chess Programs=
* [http://brooknet.no-ip.com/~lex/public/zx81/zx81_assembly_instructions.pdf ZX81 Assembly Instructions] (pdf)
* [http://www.classiccmp.org/cini/pdf/random/Timex-Sinclair%20ZX81%20Assembly.pdf ZX81 Assembly Instructions U.S. Version for UHF Channel 33] (pdf)
* [httphttps://yourcomputeronlinemagazinesfromthepast.wordpressfandom.com/tag/brendon-gorewiki/ Brendon_Gore Brendon Gore] ('''1982'''). ''[http://yourcomputeronline.wordpress.com/2011/02/27/interview-one-degree-in-artic/ Interview-One Degree In Artic]''. [[Your Computer]], [http://yourcomputeronline.wordpress.com/2011/02/23/may-1982-contents-and-editorial/ May 1982]* [[David Horne]] ('''1982'''). ''[http://yourcomputeronline.wordpress.com/2011/05/24/zx-81-disassembler/ ZX-81 Disassembler]''. [[Your Computer]], [http://yourcomputeronline.wordpress.com/2011/04/20/july-1982-contents-and-editorial/ July 1982]* [http://yourcomputeronline.wordpress.com/tag/stuart-nicholls/page/3/ Stuart Nicholls] ('''1982'''). ''[http://yourcomputeronline.wordpress.com/2012/09/22/zx-81-games-writing/ ZX-81 Games Writing]''. [[Your Computer]], [http://yourcomputeronline.wordpress.com/2011/11/13/november-1982-contents-and-editorial/ November 1982]* [[David Horne]] ('''1982'''). ''[http://yourcomputeronline.wordpress.com/2012/10/21/chess-in-1k/ Chess in 1K]''. [[Your Computer]], [http://yourcomputeronline.wordpress.com/2012/10/04/december-1982-contents-and-editorial/ December 1982]* [[David Horne]] ('''1983'''). ''ZX-81 Chess''. [[Your Computer]], [http://yourcomputeronline.wordpress.com/2012/11/03/january-1983-contents-and-editorial/ January 1983]* [[David Horne]] ('''1983'''). ''[httphttps://users.ox.ac.uk/~uzdm0006/scans/1kchess/ Full ZX-81 Chess in 1K]''. [[Your Computer]], February 1983
=Forum Posts=
