DECwriter

They were typically used in a fashion similar to a teletype, with a computer output being printed to paper and the user inputting information on the keyboard.

Versions lacking a keyboard were also available for use as computer printers, which eventually became the only models as smart terminals became the main way to interact with mainframes and minicomputers in the 1980s.

The first three were physically similar, large machines mounted on a stand normally positioned above a box of fanfold paper.

[1][a] Also known by its model number, LA30, it was one of the earliest dot matrix printers to be introduced to market, only months after the seminal Centronics 101 that May at the Spring Joint Computer Conference.

[3] Mechanically, the machine was 2 by 2 feet (0.61 by 0.61 m) and came mounted on robust legs that raised the keyboard to standard desk height with the top 31 inches (790 mm) from the ground.

[3] Normally, a box of fanfold paper would be placed below the printer mechanism and feed upward though a slot in the bottom of the stand.

The entire front cover lifted upward to provide access to the printing mechanism, both for basic maintenance and for feeding in new paper.

[4] DEC suggested leaving 16 inches (410 mm) behind the system to provide enough room to swing it fully open.

[5] In June 1972, DEC introduced two new versions of the DECwriter, the LA30A which lacked a keyboard and was used as a dedicated printer, and the LA30-E which added an RS-232 interface option, the "E" standing for the new name for the port, EIA-232.

[7] A replacement for the original product line was announced in August 1974 with the introduction of the DECwriter II series and its first model, the LA36.

This had the added advantage that the host computer did not have to insert fill characters, which in turn led to simpler interfacing requirements and reduced device driver complexity.

[12] In November, the same basic mechanism was used as the basis for new versions of the LA35 and LA36, differing primarily in using serial ports which made them easier to connect to DEC systems.

The printer electronics examined the data, skipping over blank areas at high speed, and optimizing printing in both directions by reading backward through the buffer where appropriate.

In contrast to the earlier models, which were large standalone units on their own floor-standing pedestals, the IV series were small desktop systems that looked like contemporary electric typewriters, notably the IBM Selectric.

They were slow, at 30 cps, and were not intended as outright replacements for the III series, which were more suited to unattended computer-room console terminal operation.

The system could support two plug-in cartridges and as many as three internal ROMs (bare chips), to allow up to five character sets at a time.