Viper 2.08 User's Guide download pdf (Page 37)

VIP

TINY

BASIC

MACHI$TE

LANGUAGE

SUBROUTINE

by

Andrew

A.

Modla

SeveraL vlP

computer

hobbyists have

expressed

a desj,re

to

call

nachine language

prograns

from

TINY

BASIC.

Although

hooks to

machi.ne

language

programs

were not desigred

into

TINY

BASIC due

to

space

limitationsr

there

is

a

way to

execute machine

language

prograns.

The

technique

fakes

a

new statement

tree and

when

executed by BASIC,

call-s

the machine

language

program.

Statements

have

the

following

internal

formatr

Binary

line

No.

i

!

a

a

Length

of

Statement

!

Statement

;

i

type

code

!

D

End

of

Statement

2

The

machine language

program

resides in the source

statement area.

To

eonstruct

a machine language

progratn,

do the

following steps:

f

)

Clear

the

statement

area

by tlrying

NEW.

Z)

Enter

the

following

two BASIC

statements:

1

G0r010

2

REM

3)

Holding down

Key E

enter

the VIP

operating

system

by

turning

on

the RUN

switch.

You will

be

modifying

memory

as

follows:

S

S

ourc

e

i

tatement

!

ADDRESS

ffi

L2T3

L2T4

LZI|

to

1232

1233

L234

1zFF

DATA

1300

fhis is

the

new

free

memory

address

ED

l,ine

2

statement

length

Cll

Machine language

statement

tlpe

4E

PrintabLe

Character E

(fiffer)

0E

Causes

inner

interpreter

to

enter

machine

language

Your

machine

language

program

starts

here

0D End of statement

code

The

machine

language

program

must end with DO 03 08

99

which

cannot

extend. beyond.

location 12FE.

This

means

you

have

L99

decinal bytes

available for

your

machine

language

subroutine.

00

and 0D

cannot

be

used

in

your

ML

program.

To

load

00

into

D

use

9t

(cnr

1).

ll)

Holding down the

baekspace key

on

your

ASCII

keyboard,

turn

on

the

run

switch.

This

proeedure

prevents

the

loss

of

your

BASIC

prograrn.

Add

the

following

line

r

3

REltrRN

Your

BASIC

program

begins with

line

10.

You

call the

machine

language

program

with

a

GOSUB 2.

2

,

OB/O9 ,'3'?

1 2 ... 32 33 34 35 36 37 38 39 40 41 42 ... 52 53

Comments to this Manuals

No comments