Laser 128 - Usr

BASIC COMMANDS AND STATEMENTS
3.63 USR
Purpose: This command specifies a
parameter of an assembly
language subroutine.
Format: USR (n)
Comments: n is an arithmetic expression.
When USR is encountered, the
arithmetic expression is
evaluated and placed in the
floating point accumulator, and
a JSR to location $0A is
performed which must then
contain a JUMP to the
beginning location of the
machine-language subroutine.
An R TS machine instruction
should be executed at the end of
the machine language
subroutine.
Example: ] CALL-151
* OA : 4C IO 03
* 310 : 6C
* E003G
] PRINT USR (9) * 12
108
]
A JUMP $310 instruction is
placed at location $0A and RTS
instruction at $310.
II-98