2.8.3 PEEK
I Format I
Function
Example
PEEK (ad)
PEEK@ (ad)
ad
.....
Address in decimal
or
hexadecimal
notation
(0
to
65535
or
$0000
to
$FFFF)
This function returns the
contents
of
the specified address
as
a decimal number from
0 to 255. Use
the
PEEK@ format to PEEK a user RAM area following 53248
($DOOO).
The following program displays data stored in
the
area from
40960
($AOOO)
to
40975 ($AOOF).
10
FOR
AD=
40960
TO
40975
20
9
PEEK
CAD)
30
NEXT
AD
2.8.4
USR
..................................................................
~
..........
(Abbreviated format:
U.)
Format
Function
USR (ad)
USR (ad, x$)
ad
.....
Address (decimal
or
4-digit hexadecimal)
x$
....
. String data
This
is
a special function which transfers control
to
a machine language program
which starts
at
the specified address.
As
with CALL ad, so control
is
returned
to
the
statement
following the USR function
if
the machine language program includes a
return instruction
(RET
or
RET '-' cc).
When x$ is specified, the starting address
of
the memory area containing x$
is
loaded
into
the DE register, then the length
of
x$ is loaded
into
the B register before
the
machine language program
is
called. This makes it possible for a BASIC program
to pass string data to a machine language program.
--------------------
----
-----------------------------------------------93
To Next Page
Loading...
