<P> The invention of the Intel 8080 microprocessor chip in April 1974 made practical the development of the (relatively) affordable mass - market microcomputer . In the USA this first appeared in early 1975 in the form of an unassembled kit, the Altair 8800; shortly afterward pre-assembled Altairs were offered . The sudden popularity of desktop computers happened because the 8080 CPU could represent and manipulate 256 discrete values in its 8 - bit registers . Thus the 7 - bit ASCII standard for the representation of alphanumeric data became feasible for the first time in a machine much smaller and less expensive than the furniture - size minicomputers, with their processors that occupied entire circuit boards . This new class of computer was practical for serious work because it could input, process, and output alphanumeric information . It also enabled sophisticated programs such as database managers and BASIC interpreters to become available to a larger market consisting of people possessing lesser technical skills . </P> <P> Soon after, other companies entered the market with similar, ready - to - run microcomputers like the IMSAI 8080 . These sold in the tens of thousands, surprising everyone in the industry . Beyond businesses and hobbyists, however, these computers were not widely used because (in the early days) they lacked conveniences like video displays and keyboards, required programming skills at the machine code level, and systems large enough for serious work cost many thousands . </P> <P> The very first home computer was the Compucolor by Compucolor Corporation in 1976, soon followed by the Compucolor II which was made by Intelligent Systems Corp . They used the 8080 but otherwise sported very advanced features, including RAM starting at 8 KB, expandable up to 32 KB, 64 column by 32 line color CRT display, a professional keyboard, an enhanced BASIC interpreter, and a built - in floppy disk drive . It only sold a few thousand units, however, and the company went bust not long after . </P> <P> In 1975 two new microprocessors were developed that were easier and less expensive to implement than the 8080: the MOS Technology 6502 and Zilog Z80 . In 1977 three companies decided to use this new technology to develop and market affordable, fully assembled, easy - to - use, programmable computers for individual users in their businesses and homes . These were the Commodore PET, Apple II, and TRS - 80, which Byte magazine christened the "1977 Trinity". These comprise the First Wave of home computers . </P>

When were personal computers first sold to the public