Apple IIe - Page 307

Appendix
I
307
SCRN
($F871/63601)
A=
color
of
block
X =
--
Y = - -
SCRN reads
the
color
value
at a specific
location
on
the
low
resolution
graphics screen. SCRN
places
this value
into
the
accumulator.
The
accumulator
shold
be
loaded
with
the
hori-
zontal
position.
The Y-register
should
be
loaded
with
the
vertical
position
.
SETCOL
($F864/63588) A =
--
X =
--
Y = - -
SETCOL
sets
the
current
low
resolution
color
to
the
value
in
the
accumulator.
The
colors
and
their
corresponding
values
are
listed
in
Table
6-1.
VLINE
($F828/63528) A =
??
X =
--
Y =
--
VLI
NE
plots
a
vertical
string
of
pixels
of
the
color
set
by
SETCOL
or
NEXTCOL.
VLINE
is
used
with
the
low
resolution
display.
Prior
to
calling
VLINE,
the
accumulator
must be
loaded
with
the
top
vertical
coordinate;
the
memory
location
$20
must be
loaded
with
the
bottom
vertical
coordinate;
and
the
Y-register
must be
loaded
with
the
horizontal
coordinate
.
WSI
($F3F2/62450)
A=??
X =
??
Y =
??
WSI
clears
the
currently
used
high
resolution
screen.
WSI
clears
all
192
lines
whether
or
not
a
text
window
is
being
used.
WSl1
($F3FA/62454)
A=??
X =
??
Y =
??
WSl1
sets
the
currently
used
high
resolution
screen
to
the
most
recently
plotted
color.
The
subroutine
will
not
work
from
BASIC
unless
preceded
by a
plot.