Entering A Graphics Mode - Epson FX-80 User Manual

page or even an entire line for your graphics figures. In fact, you can
reserve as little or as much space on the page as you like for a figure-
and position it anywhere on the page!
Entering a Graphics Mode or . . . Reservations required!
For each row of a graphics figure, you must first enter a Graphics
Mode and then tell the printer the number of columns you wish to
print on that line. In ordinary Graphics Mode, you can print up to 480
columns of dots across an 8-inch page; higher density modes use more
columns. The height of a figure depends on the number of passes used;
it can can be pages long-or only a few dots tall.
So while you are telling the printer that you're going to print
graphics, you also tell it how many columns to print in each horizon-
tal row. Here is the format for making this reservation:
LPRINT CHR$(27) "K"CHR$(n
1
)CHR$(n
2 ) ;
The (ESC) "K" selects Graphics Mode (which uses what we'll call
"normal" density for now). The two numbers (n
1
and nJ determine the
number of columns reserved for graphics.
Why two numbers instead of one? As usual, greed is at the root.
Wouldn't you like to be able to print a figure across the entire width of
the page if you chose? Of course you would! And an 8-inch page can
hold up to 480 normal-density graphics dots. Unfortunately, since the
BASIC CHR$ function is limited to numbers from 0 to 255, we can't
send a number as large as 480 to the printer. Carumba!
That's where the second number fits in. The two numbers work in
concert to send
very
large numbers to the printer. The first number
(n
1 )
indicates a number of columns (from 0 to 255), as you'd expect. A
255 in that position means "reserve 255 columns for graphics." Thus
any figure less than half a page wide can be handled easily by the first
number alone. In this case, we pacify the printer, which still expects a
value for the second number (nJ, with a O.
Often a figure needs more than half a page. To reserve more than
255 columns for graphics, the second number (n
2 )
must be greater than
O. But n
2
does not represent single dots; it represents bunches of 256
dots. Using a 1 in the second position means "reserve one bunch of 256
dots plus whatever is in the first number." A 2 in that spot means
"reserve 512 dots plus ... " and so on-up to 7 times 256 (or 1792)
dots of reserved width for the n
2
portion.
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