 thumb|300px|the 1977 apple ii, popular among retrocomputing hobbyists. retrocomputing is the use of older computer hardware and software in modern times. retrocomputing is usually classed as a hobby and recreation rather than a practical application of technology; enthusiasts often collect rare and valuable hardware and software for sentimental reasons. however, some do make use of it. retrocomputing often starts when a computer user realizes that formerly expensive fantasy systems like ibm mainframes, digital equipment corporation (dec) superminis, or silicon graphics (sgi) workstations have become affordable on the used computer market, usually in a relatively short time after the computers' era of use. many hobbyists have personal computer museums, with collections of working vintage computers such as apple iis, ibm pcs, zx spectrums, atari, commodore, amigas and bbc micros. early personal computers based on the s-100 bus are also very popular among collectors, as well as a wide variety of machines running the cp/m operating system, such as kaypros and osbornes. however, many users use emulation software on more modern computers rather than using real hardware, in order to enjoy the experience, while preserving the aging electronics of the original. this is not considered to be retrocomputing by some, as it is rather an application of modern computer hardware. a third option is the use of home computer remakes, dedicated appliances, which do the emulation using dedicated hardware.  ==historical retrocomputing== a more serious line of retrocomputing is part of the history of computer hardware. it can be seen as the analogue of experimental archaeology in computing. some notable examples include the reconstruction of babbage's difference engine (more than a century after its design) and the implementation of plankalkÃ¼l in 2000 (more than half a century since its inception). =="homebrew" computers== some retrocomputing enthusiasts also consider the 'homebrewing' (designing and building of retro- and retro-styled computers or kits), to be an important aspect of the hobby, giving new enthusiasts an opportunity to experience more fully what the early years of hobby computing were like. there are several different approaches to this end. some are exact replicas of older systems, and some are newer designs based on the principles of retrocomputing, while others combine the two, with old and
Apple_Inc. Retrocomputing