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9f71939934
Correct details about input/output formats and provide more thorough description of character example.
169 lines
5.3 KiB
Plaintext
169 lines
5.3 KiB
Plaintext
It's strongly believed that cas is a "character assembler". The input
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describes character shapes, and the output is data for GRAPHICS-2.
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CAS INPUT SYNTAX
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================
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: means record following string as a label.
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x means following moves are invisible.
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v means following moves are visible.
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r means end, output label=x-b+number.
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All other commands are character pairs denoting y,x coordinates in a
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14x16 character raster. Draw a line to that coordinate. Vertical
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coordinates are a-p, and horizontal are a-n. aa is upper left and pn
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is lower right. Characters reside on the base line from ma to mn
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(characters like p and q descend below this line). All characters end
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with a "x mn r" sequence to move to the beginning of the next character.
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CAS OUTPUT
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==========
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The output for each character is:
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The label x:
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18-bit octal words. Each word is three 6-bit incremental moves.
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Each incremental move consists of three fields: a 2 bit distance field,
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a 1 bit visibility field, a 3 bit direction field.
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If the visibility field is a 0 nothing is drawn, if it is a 1 a line is
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drawn. The distance field + 1 denotes how many pixels to move in a certain
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direction. The 2 bit direction field is limited to values in the range 0..3,
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but by adding 1, the actual distances denoted are in the range 1..4.
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The 3 bit direction field with values in the range 0..7 is to be interpreted
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according to this diagram and table:
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y
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^ value direction
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7 0 1 ----- ---------
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| 0 up
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| 1 up right
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| 2 right
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6---+---2>x 3 down right
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| 4 down
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| 5 down left
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| 6 left
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5 4 3 7 up left
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label=x-b+number. Number is 01, six bits saying how many moves, and
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10 zeroes.
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EXAMPLE
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=======
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Input:
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:lbk
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x
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ai
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v
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af
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mf
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mj
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x
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mn
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r
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This character is labeled "lbk" (left bracket). Move invisibly to
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"ai" near upper right. Draw line left to "af". Draw down to "mf".
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Draw right to "mj". Invisibly move to "mn" beyond lower right. End.
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This can be interpreted in a grid starting a location ma (row m, column a)
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denoted by a 0, and each succeeding move indicated by an increasing number:
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abcdefghijklmn
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a.....2..1.....
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b..............
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c..............
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d..............
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e..............
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f..............
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g..............
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h..............
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i..............
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j..............
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k..............
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l..............
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m0....3...4...5
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n..............
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o..............
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p..............
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Output:
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x:
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0010101
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0010101
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0010160
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0567474
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0747262
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lbk=x-b+0236000
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01 means move diagonally up and right one step; do this eight times.
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60 means move up four steps. 56 means draw left three steps. 74
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means draw down four steps. 72 means draw left four steps. 62 means
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move left four steps.
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0236000 means there are 15 moves, or 6-bit bytes.
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0236000 in binary is 010011110000000000, and shifting this value
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10 bits to the right gives 01001111, where only the 6 least significant
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bits indicate the number of moves, i.e. 001111 or 15 in decimal.
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The following explanation separates out each move onto its own line.
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Further it decodes each move into binary, and separates out and interprets
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the three distance, visibility and direction fields. Finally each line
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ends with a comment indicating which input command generated the output move:
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move move move dist vis direc dist vis direc input
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number octal binary binary binary binary decimal text text command
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------ ----- ------ ------ ------ ------ ------- ---- ---- -------
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1 001 000001 00 0 001 1 false up right ai
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2 001 000001 00 0 001 1 false up right ai
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3 001 000001 00 0 001 1 false up right ai
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4 001 000001 00 0 001 1 false up right ai
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5 001 000001 00 0 001 1 false up right ai
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6 001 000001 00 0 001 1 false up right ai
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7 001 000001 00 0 001 1 false up right ai
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8 001 000001 00 0 001 1 false up right ai
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9 060 110000 11 0 000 4 false up ai
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a 056 101110 10 1 110 3 true left v af
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b 074 111100 11 1 100 4 true down mf
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c 074 111100 11 1 100 4 true down mf
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d 074 111100 11 1 100 4 true down mf
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e 072 111010 11 1 010 4 true right mj
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f 062 110010 11 0 010 4 false right x mn
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This can be interpreted on a grid by starting at ma (row n, column a)
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denoted by a 0 and following the moves denoted by their corresponding
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move number. Note that after the final move, f, the location being
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outside of the character box corresponds to the location ma of the
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next character to the right. To the right is the same character where
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x:s denote drawn pixels and . denote undrawn pixels.
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abcdefghijklmn abcdefghijklmn
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a.....a..9..... a.....xxxx.....
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b.............. b.....x........
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c.............. c.....x........
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d.............. d.....x........
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e.....b..8..... e.....x........
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f.......7...... f.....x........
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g......6....... g.....x........
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h.....5........ h.....x........
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i....4c........ i.....x........
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j...3.......... j.....x........
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k..2........... k.....x........
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l.1............ l.....x........
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m0....d...e...f m.....xxxxx....
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n.............. n..............
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o.............. o..............
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p.............. p..............
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