Source : Free On-Line Dictionary of Computing

tn3270
     
        A program, similar to {telnet}, used to connect to remote
        {IBM} {mainframe} {host}s, many of which do not understand
        telnet.  The program emulates a {3270}-type terminal.
     
        For many tn3270 versions, the "clear screen" function is
        activated by typing Control-Z.  When logged on to an IBM host
        and "HOLDING" or "MORE..."  appears at the lower right corner
        of the screen, the "clear screen" function must be entered to
        display the next screen.  tn3270 emulations usually include
        {function key} definitions.
     
        (1994-11-03)