DATA DISC SYSTEM MANUAL

	To  use  the  (limited)  graphics  features  on the Data Disc
display system, one first writes a  program  in  Data  Disc  code.  A
description  of the hardware of the device may be found on DD[1,TED].
The system sends this code out directly with little modification. The
only  changes  the  system  makes  to  the code are that you may only
select your own channel, or one of the  'free'  channels  (30  to  37
octal). If you select any other channel, it will be changed into your
channel number.  The page printer UUOs are the same (PPYPOS,  PPXSIZ,
etc)  except that DPYCLR does not erase your screen. You may send out
your code with the UPGIOT if you are on a Data Disc console, or  with
PGIOT  3, if you are on a Data Disc or III console. The format of the
code is like III code except that you do not put a spare zero at  the
front  of  your  code. PGIOT 3, is the same format as the UPGIOT, but
always goes to Data Disc. There is no such thing as pieces  of  glass
on the Data Disc displays (you have to superimpose displays yourself)
so various UUOs like PGSEL and PGACT are essentially  no-ops.  UPGMOV
and  UPGMVM  are  illegal. All user graphics are sent out with the 20
bit in the CONO (forced field) on.
	There  are  three  new  commands  to the line editor that are
relevant if you happen to be on a Data Disc display.   <esc>C  clears
your  screen  entirely.   <esc>-C  erases it to solid white (green?).
<esc>P refreshed your page  printer.    <esc>R  refreshes  your  line
editor. The line editor works the same as with III.
	Another amusing feature which you may have  noticed  is  that
system  loaded messages are not printed on any displays. Plus, if you
log out or detatch and leave the display idle for a minute or so,  it
resets  the  display  to  virgin  state.   Internally, this means the
300-odd words of DPY storage is  released.  Externally,  on  III  the
display goes away, on Data Disc, your page printer position is at the
top of the screen.  You can get new storage  set  up  by  typing  any
character.