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From 1975 to 1977, most microcomputers, such as the [[KIM-1|MOS Technology KIM-1]], the [[Altair 8800]], and some versions of the [[Apple I]], were sold as kits for do-it-yourselfers. Pre-assembled systems did not gain much ground until 1977, with the introduction of the [[Apple II]], the Tandy [[TRS-80]], the first [[SWTPC]] computers, and the [[Commodore PET]]. Computing has evolved with microcomputer architectures, with features added from their larger brethren, now dominant in most market segments.
A NeXT Computer and its [[Object-oriented programming|object-oriented]] development tools and libraries were used by [[Tim Berners-Lee]] and [[Robert Cailliau]] at [[CERN]] to develop the world's first [[web server]] software, [[CERN httpd]], and also used to write the first [[web browser]], [[WorldWideWeb]].
Systems as complicated as computers require very high [[reliability engineering|reliability]]. ENIAC remained on, in continuous operation from 1947 to 1955, for eight years before being shut down. Although a vacuum tube might fail, it would be replaced without bringing down the system. By the simple strategy of never shutting down ENIAC, the failures were dramatically reduced. The vacuum-tube [[Semi-Automatic Ground Environment|SAGE]] air-defense computers became remarkably reliable – installed in pairs, one off-line, tubes likely to fail did so when the computer was intentionally run at reduced power to find them. [[Hot plugging|Hot-pluggable]] hard disks, like the hot-pluggable vacuum tubes of yesteryear, continue the tradition of repair during continuous operation. Semiconductor memories routinely have no errors when they operate, although operating systems like Unix have employed memory tests on start-up to detect failing hardware. Today, the requirement of reliable performance is made even more stringent when [[server farm]]s are the delivery platform.<ref>{{cite web |last=Shankland |first=Stephen |title=Google uncloaks once-secret server |website=CNET |date=1 April 2009 |url=https://news.cnet.com/8301-1001_3-10209580-92.html |access-date=2009-04-01 |url-status=dead |archive-url=https://web.archive.org/web/20140716084210/http://www.cnet.com/news/google-uncloaks-once-secret-server-10209580/ |archive-date=2014-07-16}} "Since 2005, its [Google's] data centers have been composed of standard shipping containers—each with 1,160 servers and a power consumption that can reach 250 kilowatts." —Ben Jai of Google.</ref> Google has managed this by using fault-tolerant software to recover from hardware failures, and is even working on the concept of replacing entire server farms on-the-fly, during a service event.<ref>{{cite web |last=Shankland |first=Stephen |title=Google spotlights data center inner workings |website=CNET |date=30 May 2008 |url=https://news.cnet.com/8301-10784_3-9955184-7.html?tag=nefd.lede |access-date=2008-05-31 |url-status=dead |archive-url=https://web.archive.org/web/20140818092344/http://www.cnet.com/news/google-spotlights-data-center-inner-workings/ |archive-date=2014-08-18}} "If you're running 10,000 machines, something is going to die every day." —Jeff Dean of Google.</ref><ref>{{cite web|title=Google Groups |url=https://groups.google.com/group/google-appengine/browse_thread/thread/a7640a2743922dcf?pli=1 |access-date=11 August 2015 |archive-url=https://web.archive.org/web/20110913014648/https://groups.google.com/group/google-appengine/browse_thread/thread/a7640a2743922dcf?pli=1 |archive-date=2011-09-13|url-status=live}}</ref>
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