Vector Graphic Extended Systems Monitor Manual de usuario descargar pdf (Pagina 19)

Extended

Systems

Monitor

User·s

Manual

us~

THE

I/O

ROUTINES

The

I/O

routines

in

the

Monitor

are

used

as

the

Main

System I/O

in

Vector

Graphic

Systems.

This

makes

software

I/O

independent

and

easily

interchangeable

between

systems.

An

example

of

how

this

is

done

is

shown

below:

INPUT

ROUTINE:

OUTPUT

ROUTINE:

INPT

OUTPT

CALL

E00CH

JZ

INPT

RET

(RETURNS

WITH

CHAR

INPUT

IN

A)

JMP'E009H

(CHARACTER

IN

A)

BREAK

TEST:

CQJTL

CALL

RET

E00CH

(RETURNS

WITH

ZERO

FLAG

SET

IF

NO

INPUT,

OR

CHARACTER

IN

A.

JUMPS

TO

MONITOR

EXECUTIVE

IF

ESCAPE

INPUT.

)

Note

that

either

the

ESC

key

will

break

to

the

Monitor,

which

provides

a

convenient

way

of

transferring

control

from any

executive

such

as

the

DOS

or

BASIC

to

the

Monitor,

but

necessitates

the

use

of

another

character

(Control

C

is

standard)

for

a

single

level

break.

The

routines

above

are

merely

given

to

illustrate

how

simple

it

is

to

use

the

Monitor

I/O

routines.

Many

programs

require

additional

instructions

to

move

the

character

to

be

output

into

the

accumulator,

or

may

require

different

flag

conditions

or

accumulator

contents

on

return

from

the

input

and Break

Test

routine,

but

the

variations

are

easily

implemented.

Rev

..

4.I2I-A

H'l/15/79

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