IBM 2741: Тарихы мен сипаттамасы

The IBM 2741 is a printing computer terminal that was introduced in 1965. Compared to the teletypewriter machines that were commonly used as printing terminals at the time,
the 2741 offers 50% higher speed, much higher quality printing, quieter operation, interchangeable type fonts, and both upper and lower case letters. It was used primarily with the IBM System/360 series of computers, but was used with other IBM and non IBM systems where its combination of higher speed and letter quality output was desirable. It was influential in the development and popularity of the APL programming language. It was supplanted, starting in the mid 1970s,
primarily by printing terminals using daisy wheel mechanisms.

The IBM 2741 came in two different varieties, one using "correspondence coding" and the other using either "PTT/BCD coding" or "PTT/EBCD coding". These refer to the positioning of the characters around the typeball and, therefore, the tilt/rotate codes that have to be applied to the mechanism to produce a given character. A "correspondence coding" machine can use type elements from a standard office Selectric (i. e. elements used for "office correspondence"). "PTT/BCD coding" and "PTT/EBCD coding" machines need special elements, and did not have as wide a variety of fonts available. or a standard command such as "login" immediately after connecting. The host software would recognize which code was used by the value of the characters it received.

The IBM 2740 is a similar terminal that lacked the interrupt feature and dialup capability, but is capable of operating in point to point, multipoint or broadcast mode. For the better use of multipoint lines, it could add a data buffer, letting the line run at 600bit/s without being constrained by the speed of the typing mechanism. Some later IBM Selectric based machines, such as the Communicating Magnetic Card Selectric Typewriter, can emulate the 2741 and be used in its place. IBM sold the underlying Selectric mechanism to other manufacturers, who produced 2741 clones at lower cost. Some of these were integrated into larger systems instead of being sold as standalone terminals. For example, a 2741 type mechanism formed the principal user interface for a series of machines from the 1960s and 1970s built in the United Kingdom by Business Computers Ltd.

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