Graphics
Even in
single-density
graphics mode,
one
8-inch line can accommodate
480
columns of graphics;
jr(
quadruple-density,
almost
2OOO
columns
can fit on the same g-inch
Bne.
Since the &inter does not use
decimal numbers larger than
255,
the graphics mode command uses
two numbers for reserving columns.
To figure
nl
and
n2,
divide the total number of columns by
256.
The result is
ir2;
the’ remainder is
nl.
Since
the command is set up
for two numbers, you must supply two even if you need only one.
When
you
need
fewer
ti&
256
cohmms,
just make
nl
the number
of
cohunns
you are
resa+@
and make
&a
zero. For example, if
you wish to
&cl
1632
c6lumns of
.gr&phica
data;
nl
should be
96
andn2shouldbebl+rusel632
-
%
+
(6
x
256).
If you are using a programming language
with
MOD (modulus) and
INT
(integer) functions, you can use the following formulas to
calculitte
rr2
<title,
in
tiki&
ti
is-
the
tad
iitixW&
~9
columns:
:
,”
nl
=
nMOD256
?I2
-
INT
(n/256)
The print& will’
i&!rpre+
f
the
ntimber
of
by&
det&&ed
‘by
nl
and
n2
as
grapWs
data;
no titter
i&at
codes
;+liey
are. This means
that you must be sure to
suppI)?
tiugh
by&s’
of
gra#&x
data or
the printer will stop and wait for more data and will seem to be
locked. If, on the other hand, you supply too much graphics data,
the excess
v&l
be interpreted and printed as regular text.
Printing
sisnple
patterns
The first ex&tple is just a’ s&&program to show you how the
graphics command, column reservation numbers, and data can be
used in a BASIC program.
4-14
Software
and Graphics
