Epson LQ-860 - Impact Printer, Руководство пользователя

Страница: 120 / 325

To find nl and n2, divide the total number of columns by 256. The
result is n2; the remainder is
n1.
Because the command is set up for
two numbers, you must supply two even if you need only one.
When you need fewer than 256 columns, just make nl the number
of columns you are reserving and make n2 a zero.
For example, if you wish to send 1632 columns of graphics data,
nl should be 96 and n2 should be 6 because 1632 = 96 + (6 x 256).
The printer interprets
the number of bytes specified by nl and n2 as
graphics data, no matter what codes they are. This means that you
must be sure to supply enough bytes of graphics data or the printer
stops and waits for
more
data and seems to be locked. If, on the
other hand, you supply too much graphics data, the excess will be
interpreted and printed as regular text.
A Simple Graphics Program
This first program is just a simple example to show how the
graphics command can be used in a BASIC program.
Type in and run the following program. Be especially careful to
include both semicolons to produce the printout below it.
10 WIDTH "LPT1:",255
20 LPRINT CHR$(27)"*"CHR$(32)CHR$(40)CHR$(0);
30 FOR X=1 TO 120
40 LPRINT CHR$(170);
50
NEXT X
Line 20 selects single-density 24-pin graphics mode (mode 32) and
also reserves 40 columns for graphics. Because 24-pin graphics
requires three bytes of data for each column, line 30 begins a loop to
supply 120 bytes of data. Line 40 contains the number 170, which
produces the first pin pattern shown in the section on pin labels, and
line 50 ends the loop.
Software and Graphics
4-13