.pa 1
.he 'DDSPUT, DDSINIT (III)'1/15/73'DDSPUT, DDSINIT (III)'
.ti 0
NAME		ddsput -- put a character on display data set
.sp
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SYNOPSIS	(file descriptor in r0)
.br
jsr	pc,ddsinit

.br
(character in r0)
.br
jsr	pc,ddsput
.sp
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DESCRIPTION	These routines
provide an interface to the Display Data Set, a peculiar
device which can be called by Picturephone sets and which
will display some of the ASCII character set and certain
other graphics on the Picturephone screen.

If the DC11 or other interface hardware is not already
set up to talk to the Display Data Set, the ddsinit_______
entry should be called with the appropriate file descriptor in r0.
On the only known DDS attached to UNIX, the associated special file
is called "/dev/ttyc".
ddsinit_______ also clears the display.

Thereafter, characters may be displayed
by calling ddsput______.
To the extent possible, ddsput______ simulates an ordinary terminal.
Characters falling to the right of the 22X22 screen
area are ignored; the 23rd line on the screen causes
the screen to be erased and that line to be put at the top
of the new display.
Certain ASCII characters are interpreted specially as follows:

.in +5
.ti -5
FF   clear screen, go to top left
.ti -5
HT   expand to right number of spaces
.ti -5
DC1  treat as reverse line feed (move N)
.ti -5
DC2  move cursor 1 place right (move E)
.ti -5
DC3  forward line feed (move S)
.ti -5
DC4  backspace 1 position (move W)
.ti -5
SO   enter graph mode
.ti -5
SI   leave graph mode
.ti -5
CR   put cursor at start of current line

.in -5
Graph mode allows display of the non-ASCII characters and
will be described when hell freezes over.

Lower-case ASCII alphabetics are mapped into upper case.
Several ASCII non-alphabetic graphics
are unavailable as well.  Also the lower right circle of
the "%" character is missing.
Also one of the circuit cards in the DDS has a crack in it and
sometimes it doesn't work.
All in all,
it is best to avoid this device.
.sp
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FILES		kept in /lib/liba.a
.sp
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SEE ALSO	AT&T writeup on DDS
.sp
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DIAGNOSTICS	--
.sp
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BUGS		yes
