ANSI/DEC VT Terminal Character Control Sequences
                     ================================================

I have found that documentation for various VT/ANSI terminal sequences is contradictory and
misleading. After extensive testing, the following sequences is what I use to obtain these
listed effects.

+--------+--------+--------------------+--------------------+----------------------------+
| Char   : Action | VT100              | VT52               : UKNC/VT52                  |
+--------+--------+--------------------+--------------------+----------------------------+
| 07     : Bell   | 07                 | 07                 : 07                         |
+--------+--------+--------------------+--------------------+----------------------------+
| 08     : Left   | 08                 | 08                 : 08                         |
| 09     : Right  | <esc>[C            | <esc>C             : <esc>C                     |
| 10     : Down   | <esc>D             | 10                 : 10                         |
| 11     : Up     | <esc>[A            | <esc>I             : <esc>I                     |
| 12     : CLS    | <esc>[2J<esc>[1;1H | <esc>H<esc>J       : <esc>H<esc>J               |
| 13     : CR     | 13                 | 13                 : 13                         |
| 30     : Home   | <esc>[1;1H         | <esc>Y<spc><spc>   : <esc>Y<spc><spc>           |
| 31,x,y : TAB    | <esc>[1+y;1+xH     | <esc>Y<32+y><32+x> : <esc>Y<32+y><32+x>         |
| 127    : Delete | 08<spc>08          | 08<spc>08          : 08<spc>08                  |
+--------+--------+--------------------+--------------------+----------------------------+
| 17,n   : COLOUR | <esc>[...m         |                    : &00+n: <esc>,160,'0'-'7'   |
|        :        |                    |                    : &40+n: <esc>,167,'0'-'7'   |
|        :        |                    |                    : &80+n: <esc>,161,'0'-'7',  |
|        :        |                    |                    :        <esc>,162,'0'-'7'   |
| 20     : Reset  | <esc>[0m           |                    :<esc>,191,163,<esc>,191,164,|
|        :        |                    |                    :<esc>,160,'7',<esc>,167,'7',|
|        :        |                    |                    :<esc>,161,'0',<esc>,162,'0' |
| 22,n   : MODE   | as VDU 20,12       |                    :<esc>,166,'1'-'4'           |
|        :        |                    |                    :      then VDU 20,12        |
+--------+--------+--------------------+--------------------+----------------------------+
| 16     : CLG    |                    |                    :                            |
| 18,a,n : GCOL   |                    |                    :                            |
| 19...  : Palette|                    |                    :                            |
| 23...  :        |                    |                    :                            |
| 24...  :        |                    |                    :                            |
| 25...  : PLOT   |                    |                    :                            |
| 26...  :        |                    |                    :                            |
| 28...  :        |                    |                    :                            |
| 29...  :        |                    |                    :                            |
+--------+--------+--------------------+--------------------+----------------------------+

Notes
-----
08 and 13 appear to be the only universal control characters. Everything else appears to
be interpreted differently by different systems. In particular, the VT100 appears to
implement 10 as NEWLINE instead of DOWN, necessitating using <esc>D. Documentation
states that <esc>[B should do DOWN, matching the pattern of <esc>A/B/C/D, but again that
also does NEWLINE instead of DOWN, necessitating using <esc>D instead.

Colour selection builds an <esc>[5;4;7;30;1;40;100m sequence as follows:
  PRINT CHR$27;"[";
  IF (A AND 16):PRINT "5;"; ELSE PRINT "25;";    :REM Flash
  IF (A AND 32):PRINT "4;"; ELSE PRINT "24;";    :REM Underline
  IF (A AND 64):PRINT "7;"; ELSE PRINT "27;";    :REM Inverse
  IF (A AND 128) THEN
    PRINT ;40+(A AND 7);                         :REM Background
    IF (A AND 8)  :PRINT";";100+(A AND 7);       :REM Bright background
   ELSE
    PRINT ;30+(A AND 7);                         :REM Foreground
    IF (A AND 8)=0:PRINT ";21"; ELSE PRINT ";1"; :REM Bright foreground
  ENDIF
  PRINT "m";

On the UKNC the RGB colour number 0,1,2,3,4,5,6,7 is mapped to 0,4,2,6,1,5,3,7.

RT11Em's VT52 implementation appears to have bugs in it. CHR$10 does NEWLINE instead
of DOWN. A VT100 <esc>[...m colour sequence appears to crash either RT11 or the
emulator.