| IBM 3270 A class of made by known as "Display Devices", normally used to talk to . The 3270 attempts to minimise the number of 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, , 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 and present a special code identifying which key was pressed. 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 called the "3270 PC" was released in October 1983. It included 3270 . is modified version of which acts as a 3270 and can be used to connect to an IBM computer over a network. See also . (1995-02-07) |
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