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Graphics
ASCII Formats
In the ASCII formats, coordinates are specified with ASCII characters
°
through 9. This means
that numeric characters generated by a simple print statement can be used to specify X,Y
pairs. The first value is used as the X coordinate, and the second as the Y coordinate.
Spaces or commas must be used to delimit the X and Y values. Excess delimiters are ignored.
Digits following a decimal point are ignored (Le. 123.456 is read as 123).
Exponential notation cannot be used. Consequently, the values must be in integer form. The
number ofbytes necessary to specify a single end point depends on the magnitude of the values.
ASCII ABSOLUTE FORMAT. The values used in the ASCII absolute format can range
between -16384 and 16383. Note that only points where X is the range
°
to 511 and Y is the
range
°
to 389 will be visible on the screen. The following example draws vectors around the
perimeter of the screen:
E
c
*
p
a
0, 0 51 1 ,0 51 1 ,389, 0 , 389 , 0 , OZ
0,389
0,0
511,389
511,0
Since no format is indicated, ASCII absolute is assumed. The
~~a"raises
the pen, which is moved
to (0,0) and lowered. Vectors are then drawn to (511,0),(511,389),(0,389), and back to (0,0).
(Note that the values are delimited by spaces or commas. The upper case
~~Z"
[a nop] terminates
the sequence. Imbedded carriage return and line feed characters are ignored.)
ASCII INCREMENTAL FORMAT. In the ASCII incremental format you can specify a delta
X and a delta Y. These values are added to the current pen position to obtain a new end point.
The first value is read as delta X and the second as delta Y. For example to draw a square 100
units on a side, the following sequence could be used:
Ec
*
P 9
100 0 0 100 -100 0 0 -100 Z
D-29
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