Retrocomputing is the current use of older computer hardware and software. 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. Occasionally, however, an obsolete computer system has to be "resurrected" to run software specific to that system, to access data stored on obsolete media, or to use a peripheral that requires that system. Vintage computer 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 Plankalkül in 2000 (more than half a century since its inception). 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 new features in the same package. Examples include: Device offered by IMSAI, a modern, updated, yet backward-compatible version and replica of the original IMSAI 8080, one of the most popular early personal systems; Several Apple 1 replicas and kits have been sold in limited quantities in recent years, by different builders, such as the "Replica 1", from Briel Computers; A currently ongoing project that uses old technology in a new design is the Z80-based N8VEM; The Arduino Retro Computer kit is an open source, open hardware kit you can build and has a BASIC interpreter.