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SINCLAIR ZX81 
home computer for a minimum prize

In 1980 the eccentric Briton Clive Sinclair already made the impossible possible by selling a home computer, the ZX80, for less then 100 British pounds, in 1981 he again hit the headlines. The successor of this tiny white computer, the ZX81, was sold for the amazing price of 70 pounds, or 100 dollar in the United States. Thus the inventor of miniature devices made it possible for hundreds of thousands of people to get acquainted with the world of the computer. About a million ZX81 computers were sold in and outside Europe.

Improvements
It was clear that the ZX80 was the mother of the ZX81. There weren't tremendous differences, although the ZX81 had some important improvements you could tell even with a minor glance at the photobooks out at the time. The 8 KB ROM (the ZX80 only had 4 KB) contained thirty extra commands of Sinclair's Basic. And the ZX81 could handle floating point numbers, an essential ability the ZX80 lacked.
Besides, it was possible to by-pass the weird ZX80 phenomenon that the display function was shortly switched off when a key was touched. By a Basic command the ZX81 could be brought into a SLOW- or a FAST-mode. In the FAST-mode the ZX81 still had the same flaw as the ZX80, but in the SLOW-mode the CPU could divert it's attention between the output to the screen and other activities. Unlike the CPU's in other home computers, the central processor in the ZX80 and ZX81 also handled the display function.

Clive Sinclair had radically changed the inside of his tiny home computers. Whereas the ZX80 contained 21 chips, in the inside of the ZX81 there were only four - an unbelievable minimum in those years. The reduction was possible because the ZX81 had and Ferranti ULA-chip, that took care for all in- and output.

Many extensions
While the ZX80 was a bit lonely, for the much more popular ZX81 many different extension options were developed. Manufactures, but also hobbyists themselves, quickly started to develop external keyboards that made typing a far less tiresome activity. And when you also had a memory pack, you suddenly had the disposal of an almost mature home computer.
Later in 1981, Sinclair produced the well-known thermal printer. Also in this device Sinclair had sought the absolute minimum ('a silver toilet-roll burner'), so other manufacturers started to sell alternatives. Memotech for instance developed a Centronics interface by which more common printers could be used.
The amount of extension options that appeared for the ZX81 was almost inexhaustible. The possibilities varied from graphical upgrades to 3.5 inch floppy drives.

Top computer Actually I already regret the few critical comments I made on the ZX81. In the early eighties Clive Sinclair provided beginning computer users with a nice home computer for an absolute minimum price. For many, particular in Europe, the ZX81 was the first home computer and thus their first contact with a new, amazing world.

Specifications of the Sinclair ZX81