BASIC
22 / Special Features
Model
111 BASIC
offers
some unusual
functions
and operations
that
deserve
special
highlighting
. Some may seem highly specialized; as
you
learn more about
programming
and begin
to
experiment with machine-language routines,
they will
take
on
more
significance .
Other
functions in the chapter
are
of
obvious
benefit
and
will
be used
often
(for
example,
the
graphics
functions)
.
Functions,
statements
and
operators described
in this
chapter:
Graphics:
SET
RESET
CLS
POINT
Error-Routine Other Functions
Functions: and Statements:
ERL INP
ERR
MEM
OUT
PEEK
POKE
POS
USR
VARPTR
SETfx,jj
Turns
on the graphics block
at
the location specified by
the
coordinates
x and
y.
For
graphics
purposes
,
the Display is divided up
into a 1
28
(horizontal) by
48 (vertical)
grid. Thex-coordinates are
numbered
from
left to
right,
to 127.
The
^-coordinates
are numbered from
top to
bottom,
to 47. Therefore the point at
(0,0)
is in the
extreme upper left
of the Display , while the point at
(
1
27
,47
) is in the extreme
lower right corner.
See the Video Display Worksheet in the Appendix.
The arguments
x and
y
may be numeric constants, variables or expressions.
They
need not be integer values, because SE7(x,y) uses the INTeger portion
ofx and
v.
SET
(x,y)
is
valid for:
0<
=
0<
=
=
x<128
=
v<48
185
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