Apple IIe - Page 228

228
Apple
lie Users
Handbook
y
1
and y
2
represent
the
range
of
row
numbers
.
x
represents
the
column
number.
The
following
VLIN
command
will
plot
every
pixel
in
column
30
from
row
4
to
row
24
.
VLIN
4,
24
AT
30
The
correct
syntax
for
an
HLIN
command
is
as
follows
:
x
1
and x
2
represent
the
range
of
column
numbers.
y represents
the
row
number
. The
following
HLIN
command
will
plot
every
pixel
in
row
14
from
column
2
to
column
37
.
HLIN
2,
37AT14
After
information
has
been
output
to
the
screen,
it
may
become
necessary
to
determine
which
color
is
displayed
at a
certain
screen
position.
The
function
SCRN takes
as
its
arguments
the
row
and
column
numbers
,
and
returns
the
color
number.
The
correct
syntax
of
the
SCRN
command
is
as
follows
:
X=SCRN
(x
,y)
x
represents
the
column
number
. y represents
the
row
number.
Upon
execution
of
the
preceding
command
, X
will
be
assigned
the
value
of
the
color
at screen
location
column
=x,
row
=y.
Uses
of
Low
Resolution
Graphics
The use
of
low
resolution
graphics
is
usually
limited
to
drawings
and
simple
charts. This
is
because
low
resolution
graphics
is
not
well-supported
in
BASIC.
Charts
Simple bar charts are
easily
implemented
by
using
low
resolution
graphics. The
text
wi
ndow
may
be
used
for
documentation
or
labels. For
example
,
the
following
program
displays
a
monthly
sales
chart.