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Printing dots
EX-800 emulation prints graphics as lines eight pin-dots high. You just
specify which of the eight dots to print for each dot-wide column.
That sounds easy, but it can be a lot of work. It means specifying an eight-
bit binary number 60 to 240 times per inch, right across the page. That’s
maybe 2000 calculations for every line! As you can imagine, graphics
software uses plenty of program loops.
The figure below shows the value of each dot on the left. The examples on
the right show how you would add up dots, to tell your printer what dots to
print for a couple of columns:
128 0
120 0
0
640
0 640
320
32 .
16 l
::
:
00
00
4e
40 0
20
0
2e
1. -
10 0
165
74
What do graphics commands look like?
To print EX-800 graphics you have to make four decisions:
l What line spacing do you want to use?
l How many dots do you want per horizontal inch? That is, what density
do you want?
l How wide is the page area on which you want to “paint” your graphics?
l What dot pattern will your data have?
Each EX-800 emulation graphics command you send does three things: it
turns on the graphics mode, specifies horizontal density, and says how many
columns wide the coming graphics data will be.
Graphics commands all print at the same vertical density or “resolution’-
72 dots per vertical inch. The commands all look the same; where they differ
is in horizontal density.
Here’s the command for the 60 dots-per-inch density:
<ESC> K nl n2
The n2 is the number of 256-column groups (either 0, 1 or 2). And the nl
represents units, the number of leftover columns.
140
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