Editing ZX80

{{Short description|1980 cheap home computer by Sinclair}}
{{Lead too short|date=June 2022}}
{{Use dmy dates|date=October 2014}}
{{infobox computer
| Photo        = ZX80.jpg
| Type         = [[Home computer]]
| release date = United Kingdom: {{Start date and age|1980|1|29|df=yes|p=yes|br=yes}}
| Discontinued = 1981
| unitsshipped = {{nowrap|100,000}}<ref>{{ cite magazine | first = Martin | last = Hayman | title = Interview – Clive Sinclair | date = July 1982 | volume = 5 | issue = 7 | magazine = [[Practical Computing]] }}</ref>
| Processor    = [[Zilog Z80|Z80]] @ 3.25–3.55&nbsp;MHz (most machines used the [[NEC μPD780C-1]] equivalent)
| storage      = External [[Compact Cassette (data)|Compact Cassette]] recorder
| Memory       = 1&nbsp;KB (16&nbsp;KB max.)
| OS           = [[Sinclair BASIC]]
| Media        = [[Cassette tape]]
| Baseprice    = £99.95 GBP (£{{Inflation|UK|99.95|1980|r=0}}; ${{To USD|{{Inflation|UK|99.95|1980}}|GBR|round=yes}} at {{CURRENTYEAR}} prices)
| predecessor  = [[MK14]]
| successor    = [[ZX81]]
| display      = [[Binary image|Monochrome]] display on UHF television
| graphics     = 24 lines × 32 characters or<br /> 64 × 48 block graphics mode
}}

The '''Sinclair ZX80''' is a [[home computer]] launched on 29 January 1980<ref>{{cite web |title=Sinclair ZX80 Launched |url=https://www.computinghistory.org.uk/det/5445/Sinclair-ZX80-Launched/ |website=Centre for Computing History |access-date=23 December 2018}}</ref> by Science of Cambridge Ltd. (later to be better known as [[Sinclair Research]]). It is notable for being one of the first computers available in the [[United Kingdom]] for less than a hundred [[Pound Sterling|pounds]]. It was available in [[Electronic kit|kit form]] for £79.95, where purchasers had to assemble and solder it together, and as a ready-built version at £99.95.<ref>{{Cite magazine|date=April 1981|title=Advertisement for Sinclair ZX81|url=https://archive.org/details/PracticalComputing1981April04|magazine=Practical Computing|volume=4|issue=4|pages=72–73}}</ref><ref name="byte198101" />

The ZX80 was advertised as the first personal computer for under £100 and received praise for its value and documentation. However, it faced criticism for screen blanking during program execution, small RAM size, and the keyboard design. It was very popular straight away, and for some time there was a waiting list of several months for either version of the machine.

== Name ==
The ZX80 was named after the Z80 processor with the 'X' meaning "the mystery ingredient".<ref>{{cite news|url=https://www.bbc.co.uk/news/magazine-12703674 |title=ZX81: Small black box of computing desire|access-date=11 March 2011 | first=Stephen | last=Tomkins | work=BBC News|date=11 March 2011}}</ref>

== Hardware ==
[[File:ZX80 platine.jpg|thumb|Inside the ZX80: Z80 is large chip in center. 4K ROM is medium-sized chip in upper right. 1K RAM is implemented by two chips in upper left. Video modulator is metal box at top.]]

Internally, the machine was designed by [[Jim Westwood]] around a [[Zilog Z80|Z80]] [[central processing unit]] with a [[clock speed]] of 3.25&nbsp;MHz, and was equipped with 1&nbsp;[[Kilobyte|KB]] of [[static RAM]] and 4&nbsp;KB of [[read-only memory]] (ROM). It had no sound output.<ref>{{cite book | url = https://ia600501.us.archive.org/14/items/the-zx80-companion/TheZX80Companion%282ndEd%29.pdf | title = The ZX80 Companion | last1 = Maunder | first1 = Bob | last2 = Trotter | first2 = Terry | last3 = Logan | first3 = Ian | date = 1980 | publisher = LINSAC | access-date = 29 Dec 2024 | language = en | pages = 7 | quote = The [television] set should be tuned to channel 36 UHF by means of the normal tuning controls. There is no sound output so the volume should be set to minimum.}}</ref>

The ZX80 was designed around readily available [[transistor-transistor logic|TTL]] ICs, without any custom chips; the only proprietary technology was the [[firmware]].<ref>{{cite web | url = https://www.8bity.cz/files/zx80const.pdf | title = Sinclair ZX80 assembly instructions | author = Sinclair Research Ltd.  | date = 1980 | website = Martinův 8-bitový blog | access-date = 29 Dec 2024 | language = en | pages = 7-8 }}</ref><ref>{{cite book | url = https://ia600501.us.archive.org/14/items/the-zx80-companion/TheZX80Companion%282ndEd%29.pdf | title = The ZX80 Companion | last1 = Maunder | first1 = Bob | last2 = Trotter | first2 = Terry | last3 = Logan | first3 = Ian | date = 1980 | publisher = LINSAC | access-date = 29 Dec 2024 | language = en | pages = 90 }}</ref>

The machine was mounted in a small white plastic case, with a one-piece blue [[membrane keyboard]] on the front. There were problems with durability, reliability and overheating (despite appearances, the black stripes visible on the top rear of the case are merely cosmetic, and are not ventilation slots).<ref>{{cite magazine |last=Tebbutt |first=David |date=April 1980|title=Benchtest: The Sinclair ZX80 |url=https://archive.org/details/PersonalComputerWorld1980-04 |magazine=[[Personal Computer World]]|pages=55|access-date = 29 Dec 2024|quote=…the casing even has go-faster stripes, which look suspiciously like ventilation slots in black and white photographs (coincidence, I'm sure).}}</ref>

Video output was black-and-white, character-based.{{r|mccallum198101}} However, the [[ZX80 character set]] included some simple block-based graphics glyphs, allowing basic graphics to be accomplished, with some effort. One advantage to using monochrome video is that different colour broadcast standards (e.g. [[PAL]], [[SECAM]]) simply weren't an issue when the system was sold outside the UK.<ref>{{cite magazine |last=Tebbutt |first=David |date=April 1980|title=Benchtest: The Sinclair ZX80 |url=https://archive.org/details/PersonalComputerWorld1980-04 |magazine=[[Personal Computer World]]|pages=55|access-date = 29 Dec 2024|quote=American television (525 line) users are catered for as well; all they need to do is solder in one diode and the system is converted from 50 to 60Hz standards.}}</ref>

Display was over an [[radio frequency|RF]] [[RF connector|connection]] to a household [[television]], and simple offline program storage was possible using a [[cassette deck|cassette recorder]]. The video display generator of the ZX80 used minimal hardware plus a combination of software to generate a video signal. (Some say this was an idea popularised by [[Don Lancaster]] in his 1978 book [[TV Typewriter#TV Typewriter Cookbook|''The TV Cheap Video Cookbook'']] and his "[[TV Typewriter]]".<ref>{{ cite book | chapter-url = https://www.nvg.ntnu.no/sinclair/computers/zx80/zx80_sst.htm | chapter = A New Means To An Old End | title = Sinclair and the 'Sunrise' Technology | last = Adamson | first = Ian | author2 = Richard Kennedy | publisher = [[Penguin Books]] | year = 1986 }}</ref> However, that design didn't involve a microprocessor for video generation, and it wasn't really similar to the ZX80 in other aspects either. The ZX80 and ZX81 also employed very specific traits of the Z80 processor.)

Unlike the later follow up, ZX81, the ZX80 could only generate a picture when it was idle, i.e. waiting for a key to be pressed. When running a BASIC program, or when pressing a key during editing, the tv-display would therefore blank out (lose synchronisation) momentarily while the processor was busy. So a BASIC program had to introduce a pause for input to display the next change in graphical output,{{r|mccallum198101}} making smooth moving graphics impossible. This could be overcome only by very clever machine code tricks. These had to effectively replace the video rountines in ROM and embed the same in the normal program logic with exact timing, which is extremely cumbersome. However, a few such games were developed by skilled users or programmers later on.

== Firmware ==
The 4 KB ROM contained the [[Sinclair BASIC#4K BASIC|Sinclair BASIC]] [[programming language]], editor, and [[operating system]]. BASIC commands were not entered by typing them out but were instead selected somewhat similarly to a programmable graphing calculator - each key had a few different functions selected by both context and modes as well as with the shift key.{{r|mccallum198101}}

== Expansion ==
[[File:Sinclair ZX80 with 8K upgrade keyboard at Powerhouse Sydney (filtered retouched).jpg|thumb|Upgraded ZX80 showing the ZX81-style replacement keyboard overlay for use with the 8K ROM]]

Other than the built-in cassette and video ports, the only provided means of expansion was a slot opening at the rear of the case, which exposed an expansion bus [[edge connector]] on the motherboard. The same slot bus was continued on the ZX81, and later the [[ZX Spectrum]], which encouraged a small [[cottage industry]] of expansion devices, including memory packs, [[printer (computing)|printers]] and even [[floppy drive]]s. The original Sinclair ZX80 RAM Pack held either 1, 2 or 3&nbsp;KB of [[Static random-access memory|static RAM]]<ref name='fjkraan'>{{cite web |title=1 to 3K byte memory expansion RAM PACK for the Sinclair ZX80 |url=https://fjkraan.home.xs4all.nl/comp/zx80/rampack.html |archive-url=https://archive.today/20130222225950/http://fjkraan.home.xs4all.nl/comp/zx80/rampack.html |url-status=dead |archive-date=22 February 2013 |website=F J Kraan |access-date=8 December 2019 }}</ref>  and a later model held 16&nbsp;KB of [[Dynamic random-access memory|dynamic RAM]] (DRAM).<ref>{{cite web |title=Ultra Rare Vintage Sinclair ZX80 16K Byte Ram Pack (Mint) |url=https://www.ebay.co.uk/i/293012513981?chn=ps&norover=1&mkevt=1&mkrid=710-134428-41853-0&mkcid=2&itemid=293012513981&targetid=595627780033&device=c&mktype=pla&googleloc=1007408&poi=&campaignid=6619152134&mkgroupid=84510981728&rlsatarget=pla-595627780033&abcId=1140496&merchantid=9752904&gclid=EAIaIQobChMIt_WWg-u05gIVRrTtCh1bRg9fEAQYASABEgJl3vD_BwE |website=Ebay |access-date=14 December 2019}}{{dead link|date=September 2021}}</ref> With software, the computer can use up to 48 KB of memory.<ref name="heuristics198206">{{Cite magazine |last=Ornstein |first=David B. |date=June 1982 |title=More Memory for the ZX80 |url=https://archive.org/details/byte-magazine-1982-06/page/n41/mode/1up?view=theater |access-date=2025-03-16 |department=Letters |magazine=BYTE |pages=40,42}}</ref>

Following the ZX81's release, a ZX81 8&nbsp;KB [[read-only memory|ROM]] was available to upgrade the ZX80 at a cost of around 20% of a real ZX81. It came with a thin keyboard overlay and a ZX81 manual. By simply taking off the top cover of the ZX80 and prying the old ROM from its socket and carefully inserting the new ROM and adding the keyboard overlay, the ZX80 would now function almost identically to the proper ZX81 – except for SLOW mode, due to the differences in hardware between the two models. The process was easily reversed to return the ZX80 to its original configuration.<ref>{{cite magazine |title=Advertisement for ZX Printer |magazine=Your Computer |date=October 1981 |volume=1 |issue=3|pages=42–43 |url=https://archive.org/details/your-computer-magazine-1981-10/page/n41 |access-date=13 December 2019}}</ref>

One common modification by hobbyist users was to attach a full-size keyboard, optionally moving the motherboard into a larger case. This had the dual advantages of making the machine easier to type on, while increasing ventilation to the motherboard.<ref>{{cite magazine |title=DK'Tronics advertisement for full sized keyboard |magazine=Your Computer |date=May 1982 |page=5 |volume=2 |issue=5 |url=https://archive.org/details/your-computer-magazine-1982-05/page/n5 |access-date=13 December 2019}}</ref>

== Versions ==
The UK version of the machine was the standard, and only changes that were absolutely necessary to sell units in other markets were made. In fact, the only real change made in most markets involved the video output frequency (the ZX80 used an external power transformer, so differences in AC line frequency and outlet were not an issue to the machine itself).  One outcome of this is that the machine had some keyboard keys and characters that were distinctly British:  {{keypress|NEWLINE}} was used instead of {{keypress|ENTER}}, {{keypress|RUBOUT}} instead of {{keypress|BACKSPACE}} or {{keypress|DELETE}}, and the character set and keyboard included the [[Pound sterling|Pound]] [[Pound sign|symbol]].

== Reception ==
The ZX80 was widely advertised as the first personal computer for under £100 GBP<ref>{{cite web|url=https://rk.nvg.ntnu.no/sinclair/computers/zx80/zx80.htm |title=ZX80 |website=Planet Sinclair }}</ref> (US$200.<ref name="byte198101">{{cite magazine | url=https://archive.org/stream/byte-magazine-1981-01/1981_01_BYTE_06-01_Hand-held_Computers#page/n119/mode/2up | title=The first personal computer for under $200. | magazine=BYTE | volume=6 | issue=6 | date=January 1981 | access-date=18 October 2013 | type=Advertisement  | page=119}}</ref>{{r|mccallum198101}}) ''[[Kilobaud Microcomputing]]'' liked the design of the preassembled version, and said that the screen flickering during input or output was annoying but useful as an [[undocumented feature]], indicating the computer functioning correctly. It praised the documentation as excellent for novices, and noted that purchasing the computer was cheaper than taking a college class on BASIC. The magazine concluded, "The ZX-80 is a real computer and an excellent value", but only for beginners who could learn from the documentation or programmers experienced with writing Z-80 software.<ref name="wszola198012">{{cite magazine | url=https://archive.org/stream/kilobaudmagazine-1980-12/Kilobaud_Microcomputing_1980_December#page/n169/mode/2up | title=The Sinclair ZX-80 Microcomputer | magazine=Kilobaud Microcomputing | date=December 1980 | access-date=23 June 2014 | last=Wszola |first=Stanley J. | pages=168–169}}</ref> ''[[BYTE]]'' called the ZX80 a "remarkable device". It praised the real-time, interactive BASIC syntax checking, and reported that the computer performed better on [[benchmark (computing)|benchmarks]] than some competitors, including the [[TRS-80 Model I]]. The magazine criticised the screen blanking during program execution, small RAM size, inadequate built-in Sinclair BASIC, and keyboard, and recommended against buying the kit version given difficulty of assembly and because purchasers did not save money. ''BYTE'' concluded that "the ZX80 might be summarized as a high-performance, very low-cost, portable personal computer system ... a good starting point".<ref name="mccallum198101">{{cite magazine | url=https://archive.org/stream/byte-magazine-1981-01/1981_01_BYTE_06-01_Hand-held_Computers#page/n95/mode/2up | title=The Sinclair Research ZX80 | magazine=BYTE | volume=6 | issue=6 | date=January 1981 | access-date=18 October 2013 | last=McCallum |first=John C | pages=94–102}}</ref>

Sales of the ZX80 reached about 50,000, which contributed significantly to the UK leading the world in home computer ownership through the 1980s. Owing to the unsophisticated design and the tendency for the units to overheat, surviving machines in good condition are sought after and can fetch high prices by collectors.<ref>{{cite web |title=Retro: Cash in on your vintage PC |url=https://www.alphr.com/features/105551/retro-cash-in-on-your-vintage-pc |website=Alphr |date=7 October 2009 |access-date=25 November 2019 |archive-date=6 December 2021 |archive-url=https://web.archive.org/web/20211206211243/https://www.alphr.com/features/105551/retro-cash-in-on-your-vintage-pc |url-status=dead }}</ref>

== Clones ==
There were also [[List of ZX80 and ZX81 clones|clones of the ZX80]], such as the [[MicroAce]],<ref name="searls198104">{{cite magazine | url=https://archive.org/stream/byte-magazine-1981-04/1981_04_BYTE_06-04_Future_Computers#page/n47/mode/2up | title=The MicroAce Computer | magazine=BYTE | volume=6 | number=4 | date=April 1981 | access-date=18 October 2013 | last=Searls |first=Delmar | pages=46–64}}</ref> and from [[Brazil]] the Nova Eletrônica/[[Prológica Indústria e Comércio de Microcomputadores|Prológica]] [[NE-Z80]] and the [[Microdigital Eletronica|Microdigital]] [[TK80]].<ref>[https://zx.interface1.net/clones/ne.html#nez80 NE Z80]</ref><ref name="MCI">{{cite web |date=2002-01-01 |title=Microdigital |url=https://www.mci.org.br/fabricante/microdigital.html |accessdate=2013-07-01 |language=Portuguese |archive-date=23 December 2017 |archive-url=https://web.archive.org/web/20171223013230/http://www.mci.org.br/fabricante/microdigital.html |url-status=dead }}</ref><ref name=":2">{{Cite web |title=Clube do TK90X |url=https://www.tk90x.com.br/Microdigital.html |access-date=2022-12-19 |website=www.tk90x.com.br}}</ref>

== See also ==
* [[ZX80 character set]]

== References ==
{{reflist}}

== External links ==
{{commons category|Sinclair ZX80}}
* [https://www.nvg.ntnu.no/sinclair/computers/zx80/zx80.htm Planet Sinclair:ZX80]
* {{cite web |url=https://www.zx-spectrum.pl/kolekcja/1-zx80-a/1-zx80-a.html |title=Showcase of Sinclair ZX80 |archive-url=https://web.archive.org/web/20081208114401/http://www.zx-spectrum.pl/kolekcja/1-zx80-a/1-zx80-a.html |archive-date=8 December 2008 }}
* [https://web.archive.org/web/20150707050636/http://www.mango-a-gogo.com/scot/zx80/zx80.htm Scot's ZX80 site via archive.org]

{{Sinclair computers and clones}}
{{Authority control}}

[[Category:English inventions]]
[[Category:Computers designed in the United Kingdom]]
[[Category:Early microcomputers]]
[[Category:Z80-based home computers]]
[[Category:Computer-related introductions in 1980]]
[[Category:Home video game consoles]]
[[Category:Products and services discontinued in 1981]]
[[Category:ZX80]]