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     INTRO(9)                                                 INTRO(9)

          intro - introduction to jerq-related software

          Section 9 of this manual lists software for running or
          supporting Teletype DMD-5620 terminals, the current
          implementation of the `jerq' graphics terminals.
          Subsections 9.1-9.7 mirror the purposes of the preceding
          sections 1-7, with 9.1 being commands, 9.6 being games, etc.

          The only `real' 5620 commands are 32ld, which loads programs
          into the terminal, and mux, which starts the characteristic
          `layer' or window system.  The other commands in section 9
          either run on Unix or within mux layers.

          A layer is technically a virtual terminal, but is almost
          indistinguishable in software from a real terminal; in par-
          ticular, the interface described in ttyld(4) applies to lay-
          ers, except for the additional editing capabilities dis-
          cussed in mux(9.1).

          The commands in sections 9.1 and 9.6 run on Unix, but most
          also call 32ld to `down-load' a program that replaces the
          default terminal process running in the layer, that is, the
          command's controlling teletype.  To Unix the interface is
          still that of a terminal; in particular /dev/tty is always
          connected to the layer.  The default mux terminal program
          implements the teletype function itself, but when a program
          is down-loaded a teletype line discipline is pushed on the
          stream (see stream(4) and ttyld(4)). Some commands may sim-
          ply emulate other terminals by down-loading a terminal pro-
          gram (see term(9.1); others, such as the text editor
          jim(9.1), are really two programs - one on Unix and one in
          the layer - communicating using standard input/output on
          Unix and sendchar/rcvchar in the terminal; see request(9.2).

          There is an identity between bitmaps and layers in the
          graphics software.  The objects of jerq graphics are bit-
          maps.  The primitives that operate on layers are aliased to
          the bitmap primitives, and the data structures are isomor-
          phic.  When running under mux, a programmer need not con-
          sider layers as graphical objects at all; the operating sys-
          tem checks the arguments to the graphics primitives and dis-
          patches the appropriate operator depending on the type of
          the argument.  Except in stand-alone software, layers are an
          invisible implementation detail.

          32ld(9.1), mux(9.1), stream(4), pt(4)