The DECwriter series was a family of computer terminals from Digital Equipment Corporation (DEC). 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. In contrast to teletypes, the DECwriters were based on dot matrix printer technology, one of the first examples of such a system to be introduced. 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.
There were four series of machines, starting with the original DECwriter in 1970, the DECwriter II in 1974, DECwriter III in 1978, and the final DECwriter IV in 1982. The first three were physically similar, large machines mounted on a stand normally positioned above a box of fanfold paper. They differed primarily in speed and the selection of computer interfaces. The IV was significantly different, intended for desktop use and looking more like an IBM Selectric typewriter than a traditional printer. Most models were available without a keyboard for print-only usage, in which case they were later known as DECprinters.
The DECwriters were among DEC's best-selling products, notably the II and III series.
DECwriter
The original DECwriter was introduced in November 1970 at the Fall Joint Computer Conference. 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. At the time, most small computer systems were accessed using surplus or new teletype units, such as the popular ASR-33. The LA30 was intended to be used in the same general fashion (although it lacked any ability to read or output punched tape). As such, its only computer interface was a 30 mA current loop, as used on teletype machines, with the explicit goal of "having been designed to replace the standard Teletype Model 33, 35 and 37 KSR".
The LA30 used a 64-character ASCII-based character set, lacking lower-case characters and printing them in upper-case. It used a 7-pin print head with glyphs in a 5x7 grid. It normally printed 80-column lines on standard inch wide tractor feed paper. It could print up to 30 characters per second (cps), matching the maximum interface speed of 300 bit/s (30 cps, assuming one start and one stop bit). The interface could also run at 110 and 150 bit/s. However, carriage returns required of a second, during which time the host computer had to send data it would know would not be printed, the so-called "fill characters" that were commonly required by printers of the era.
Mechanically, the machine was and came mounted on robust legs that raised the keyboard to standard desk height with the top from the ground. 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 casing around the keyboard was curved, somewhat similar to the ADM-3A. The entire front cover lifted upward to provide access to the printing mechanism, both for basic maintenance and for feeding in new paper. DEC suggested leaving behind the system to provide enough room to swing it fully open.
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. A later addition was the LA30-P, the "P" referring to the addition of a parallel Centronics port, which had become an almost universal de facto standard by the mid-1970s.
DECwriter II
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. The LA36 used the same basic printing mechanism as the LA30, and was physically similar although smaller and more rectangular. Like the LA30, the LA36 was also offered in a keyboard-less printer-only model, in this case known as the LA35.