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.TH INTRO 9
.SH NAME
intro \- introduction to jerq-related software
.SH DESCRIPTION
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.
.PP
The only `real' 5620 commands are
.I 32ld,
which loads programs into the terminal, and
.IR mux ,
which starts the characteristic `layer' or window system.
The other commands in section 9 either run on Unix or within
.I mux
layers.
.PP
A layer is technically a virtual terminal,
but is almost indistinguishable in software from a real terminal;
in particular, the interface described in
.IR ttyld (4)
applies to layers, except for the additional editing capabilities discussed in
.IR mux (9.1).
.PP
The commands in sections 9.1 and 9.6 run on Unix,
but most also call
.I 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
.I /dev/tty
is always connected to the layer.
The default
.I 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
.IR stream (4)
and
.IR ttyld (4)).
Some commands may simply
emulate other terminals by down-loading
a terminal program (see
.IR term (9.1);
others, such as the text editor
.IR jim (9.1),
are really two programs \(em one on Unix and one in the layer \(em
communicating using standard input/output on Unix
and
.I sendchar/rcvchar
in the terminal; see
.IR request (9.2).
.PP
There is an identity between bitmaps and layers
in the graphics software.
The objects of jerq graphics are bitmaps.
The primitives that operate on layers are aliased to the bitmap
primitives, and the data structures are isomorphic.
When running under
.IR mux ,
a programmer need not consider layers as graphical objects
at all; the operating system checks the arguments to the graphics
primitives and dispatches the appropriate operator depending
on the type of the argument.
Except in stand-alone software, layers are an invisible
implementation detail.
.SH SEE ALSO
32ld(9.1), mux(9.1), stream(4), pt(4)