Usr - Sharp MZ-700 Basic Manual

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USR
(user)
Calls out and executes in BASIC the machine language program.
Format:
USR «address> , <input character variable> , <output character variable)
<address> : numerical data or 4-digit hexadecimal number
Abbreviated form:
U.
Explanation:
• Calls out and executes the machine language program during BASIC program
execution. This is the same as the branch command and CALL <address> to the
machine language subroutine. Consequently, when there is a return command in a
machine language program, control moves to the next statement following the
executed statement.
• At the point in time when the machine language program is called out, the value
following the <input character variable> is set in the register.
DE register: heading address of memory area of <input character variable>
B register: length of <input character variable>
IX register: address if error-processing routine is announced
• At the point in time of return from the machine language program, the value of the
data indicated by the subsequent register becomes the <output character
variable>.
DE register: heading address of memory area of <output character variable>
B register: length of <output character variable>
• If error-processing is necessary in a machine language program, the following
process occurs.
(1) An error-processing routine is established by the ON ERROR GOTO
statement in the BASIC program.
(2) An error code is substituted in the A register, and is jumped to the address
indicated by the IX register.