MELCOM81

MELCOM81 was a small computer for small and medium-sized enterprises. It was developed by Mitsubishi Electric Corporation and first marketed in 1968. As a feature, it can print a large-scale form of about 650 mm width, and can process the ledger with setting the continuous form and the cut sheet at the same time, when you separately use the form stand.

Its arithmetic unit was 1-bit type with the decimal adjust function similar to the electronic calculator, and the circuit element was composed of transistors and diodes. And its main memory was a magnetic disk unit with the capacity of 6 kilobytes. Though the magnetic disk unit was low-speed as a main memory, it was adopted because it was inexpensive. Its programming language was a machine language (COOL). To realize a sufficient processing performance with low-speed main memory, a decimal memory addressing was adopted as memory addressing. And a binary coded decimal arithmetic as arithmetic way, 12 digits and a sign in one word, a 3-address as control system, and a compound instructions were adopted, so it was possible to complete the business arithmetic processing in a single instruction. But only numerical data were supported, so this computer could be categorized into an electronic accounting machine.

A phrase "office computer" was used in the catalog of MELCOM81. This is the origin of the popular name "office computers" used for this type of computers in Japan later.