3270

1 definition found

3270 - Free On-line Dictionary of Computing (26 May 2007) :

  IBM 3270
  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.
  
     (1995-02-07)