Radio Shack TRS-80 model III Owner's Manual page 114

DISK
BASIC
Examples
NAME
Renumbers
the entire
program:
10,
20, 30,
. .
.
NAME 8000*5000*100
Renumbers
all
lines
numbered from 5000
up; the
first
renumbered
line will
become
6000, and
the
following
lines will
be incremented by
100. All
line
references within your
program
will
be
renumbered
also.
USRn
Call
to
User's External Subroutine
usR/f
(nmexp)
wtt#m
irsjieeille^ qiie of
ten available
usr
calls,
/?=B,1,2,^,9.
If /»
is
p^jttetf, zero
is
assumed.
fim&M
an integerlrom
-32768
to
32767 and
Is
passed
as
an
integer
argument
to the routine.
These
functions
(usro through USR9) transfer control to
machine-language
routines
previously defined with
DEFUSRn
statements.
When
a
urs
call
is
encountered
in
a statement, control
goes
to
the
address
specified in the
defusraz statement.
This address
specifies
the entry point
to
your
machine-language
routine.
Note:
If
you
call
a
usrh
routine before defining the routine entry point with
DEFUSRrc, an
illegal function
call
error will occur.
You
can
pass
one argument and
retrieve
one
output value directly via the
usr
argument; or
you can
pass
and
retrieve
arguments indirectly via
poke and peek
statements.
Example
1.0
DEFUSR1=&H7D00
20 REM,
MORE
PROGRAM LINES HERE
100
A=USR1<X)
The
effect
of
this
sequence
is
to:
113