IBM 3270


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IBM 3270

(hardware)
A class of terminals made by IBM known as "Display Devices", normally used to talk to IBM mainframes. The 3270 attempts to minimise the number of I/O interrupts required by accepting large blocks of data, known as datastreams, in which both text and control (or formatting functions) are interspersed allowing an entire screen to be "painted" as a single output operation. The concept of "formatting" in these devices allows the screen to be divided into clusters of contiguous character cells for which numerous attributes (color, highlighting, character set, protection from modification) can be set. Further, using a technique known as 'Read Modified' the changes from any number of formatted fields that have been modified can be read as a single input without transferring any other data, another technique to enhance the terminal throughput of the CPU.

The 3270 had twelve, and later twenty-four, special Programmed Function Keys, or PF keys. When one of these keys was pressed, it would cause the device to generate an I/O interrupt and present a special code identifying which key was pressed. Application program functions such as termination, page-up, page-down or help could be invoked by a single key-push, thereby reducing the load on very busy processors.

A version of the IBM PC called the "3270 PC" was released in October 1983. It included 3270 terminal emulation.

tn3270 is modified version of Telnet which acts as a 3270 terminal emulator and can be used to connect to an IBM computer over a network.

See also broken arrow.
References in periodicals archive ?
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Indeed in its own material, Sun says the closest equivalent to Sun Ray 1 is an IBM 3270 green screen character terminal - except that Sun Ray 1 has graphics.
Because many legacy applications have no other access mechanism than the proprietary terminals they were designed to use (for example, the IBM 3270 and 5250), the legacy information is often segregated from the rest of the enterprise's information systems.
Our planning department had been using a home-grown FoxBase application running on an IBM 3270, a slow, single-user program that did not provide the functionality we required.
Leonard's PC using the IBM 3270 emulation hardware and software.
Users could access only applications on their local mainframe through IBM 3270 terminals or personal computers on local area networks linked to athe mainframes via gateways.
And by using full screen, IBM 3270 emulating RF terminals, Glaxo didn't need to rewrite application software because it was previously used on its hardwire fullscreen terminals.
OCLC Gateway Software is compatible with many kinds of computer equipment, ranging from OCLC workstations and PCs running PASSPORT (OCLC communications software), to Apple and other computers running VT100 emulation packages, IBM 3270 terminals, commonly used local system terminals, and other public-access machines.
Programs written for IBM 3270 dedicated terminals seem to make extensive use of function keys which must be mapped to the existing keyboard.
Also, this network is connected to the mainframe using a Netway 1000 box that provides IBM 3270 emulation.