It's strongly believed that cas is a "character assembler".  The input
describes character shapes, and the output is data for GRAPHICS-2.


CAS INPUT SYNTAX
================

: means record following string as a label.

x means following moves are invisible.

v means following moves are visible.

r means end, output label=x-b+number.

All other commands are character pairs denoting y,x coordinates in a
14x16 character raster.  Draw a line to that coordinate.  Vertical
coordinates are a-p, and horizontal are a-n.  aa is upper left and pn
is lower right.  Characters reside on the base line from ma to mn
(characters like p and q descend below this line).  All characters end
with a "x mn r" sequence to move to the beginning of the next character.


CAS OUTPUT
==========

The output for each character is:

The label x:

18-bit octal words.  Each word is three 6-bit incremental moves.
Each incremental move consists of three fields: a 2 bit distance field,
a 1 bit visibility field, a 3 bit direction field.

If the visibility field is a 0 nothing is drawn, if it is a 1 a line is
drawn.  The distance field + 1 denotes how many pixels to move in a certain
direction.  The 2 bit direction field is limited to values in the range 0..3,
but by adding 1, the actual distances denoted are in the range 1..4.
The 3 bit direction field with values in the range 0..7 is to be interpreted
according to this diagram and table:

            y
            ^			value	direction
        7   0   1       	-----	---------
            |           	0	up
            |           	1	up right
            |           	2	right
	6---+---2>x		3	down right
            |           	4	down
            |           	5	down left
            |           	6	left
        5   4   3               7	up left


label=x-b+number.  Number is 01, six bits saying how many moves, and
10 zeroes.


EXAMPLE
=======

Input:

   :lbk
   x
   ai
   v
   af
   mf
   mj
   x
   mn
   r

This character is labeled "lbk" (left bracket).  Move invisibly to
"ai" near upper right.  Draw line left to "af".  Draw down to "mf".
Draw right to "mj".  Invisibly move to "mn" beyond lower right.  End.

This can be interpreted in a grid starting a location ma (row m, column a)
denoted by a 0, and each succeeding move indicated by an increasing number:

 abcdefghijklmn
a.....2..1.....
b..............
c..............
d..............
e..............
f..............
g..............
h..............
i..............
j..............
k..............
l..............
m0....3...4...5
n..............
o..............
p..............

Output:

   x:
   0010101
   0010101
   0010160
   0567474
   0747262
   lbk=x-b+0236000

01 means move diagonally up and right one step; do this eight times.
60 means move up four steps.  56 means draw left three steps.  74
means draw down four steps.  72 means draw left four steps.  62 means
move left four steps.

0236000 means there are 15 moves, or 6-bit bytes.

0236000 in binary is 010011110000000000, and shifting this value
10 bits to the right gives 01001111, where only the 6 least significant
bits indicate the number of moves, i.e. 001111 or 15 in decimal.

The following explanation separates out each move onto its own line.
Further it decodes each move into binary, and separates out and interprets
the three distance, visibility and direction fields.  Finally each line
ends with a comment indicating which input command generated the output move:

move	move	move	dist	vis	direc	dist	vis	direc	input
number  octal   binary	binary	binary	binary	decimal	text	text	command
------  -----	------	------	------	------	-------	----	----	-------
1       001	000001	00	0	001	1	false	up right ai
2       001	000001  00	0	001	1	false	up right ai
3       001	000001  00	0	001	1	false	up right ai
4       001	000001  00	0	001	1	false	up right ai
5       001	000001  00	0	001	1	false	up right ai
6       001	000001  00	0	001	1	false	up right ai
7       001	000001  00	0	001	1	false	up right ai
8       001	000001  00	0	001	1	false	up right ai
9       060	110000  11	0	000	4	false	up	 ai
a       056	101110  10	1	110	3	true	left	 v af
b       074	111100  11	1	100	4	true	down	 mf
c       074	111100  11	1	100	4	true	down	 mf
d       074	111100  11	1	100	4	true	down	 mf
e       072	111010  11	1	010	4	true	right	 mj
f       062	110010  11	0	010	4	false	right	 x mn

This can be interpreted on a grid by starting at ma (row n, column a)
denoted by a 0 and following the moves denoted by their corresponding
move number.  Note that after the final move, f, the location being
outside of the character box corresponds to the location ma of the
next character to the right.  To the right is the same character where
x:s denote drawn pixels and . denote undrawn pixels.

 abcdefghijklmn           abcdefghijklmn
a.....a..9.....          a.....xxxx.....
b..............          b.....x........
c..............          c.....x........
d..............          d.....x........
e.....b..8.....          e.....x........
f.......7......          f.....x........
g......6.......          g.....x........
h.....5........          h.....x........
i....4c........          i.....x........
j...3..........          j.....x........
k..2...........          k.....x........
l.1............          l.....x........
m0....d...e...f          m.....xxxxx....
n..............          n..............
o..............          o..............
p..............          p..............