Atari 800 Manuel de l'opérateur télécharger pdf (Page 17)

I

i

t

I

I

os

Dos

Empty

EdilTexl

Buffer

Emply

Dlsplay

180

Top

ol

BAM

YoUi RAM

Figure

3. Memory

tnap

with ttse

of LOMEM.

This

bumping

is accomplished

wfth

a speciat

cornmand

ca ed LOMIIM.

The

command

rs special

because

ir

must be rhe very

fir"l

command you

enler

aner

iuning

on the

computer.

Its form

is simple:

LOMEM

xxxx

g!19fiffi1

wher€ XXXX

is the

hexadecimal

address

ofth€ new

boftom

edge ofthe

edit t€xt

buffer

rpoint

A in

the mernory

mapr.

you

musl

not ser LOMf,M

to

a smaller

varue

rnan

normalty

rs. or you will

overwrite

OS data or DOS

and

.rdsh

rhe

system.

rurthermore,

ifyou set LOMIM

roo

high,

you

will have

too little room

ror your

source

Fogram.

you

must

esiirl-Iate

how much

memorv

your

obiect

cod€ will

require,

and

bum_p the

edit teni

buffer upward

by

thit"-".r,

!t""

some

more for insurance.

Then your

firsi

program

instruction

becomes:

'

10

*

=$YYYY

wherF

YYYY

is

rhe old lalue

of A given

by rhe StZr

command

before

you

turned oll

lhe compuler,

'Lrrned

ir

brck on, and

used

rhe LOMiM command

You

might wonder

why

anybody would

want

to use the LOMIM

command and

store

the object prcgram

in front

ofthe sourc€ program

instead

of behind it.

The primary

reason

ihis conunand

is

prcvided

com€s

fiom th€ fact

that the

Assembler program.

as ir

rranslares your

souice program

inro an

obiecl

pro-

gram.

uses so^me

addiiional

memory tca

ed

a symboliabJerjusr

above

rhe

edit

object

pro-

rerr

buffer. lfyou

realll wanted

io,

you.ould-fieure

jusr

how much

memorv

rhe symbol

iable

uses; ir i"

lhrep b!Ie!

tor eJch

dlsrinci Iabet olu. one bq" r"',plus

on€

bl-te for

rhe symbol

iable

usesi ir i"

lhrep bJa;!

tor eJch

each chdracler

in

€ach labpl.

Mosr

progr€mmers

$

ho doni e^joy

ngoing

our

now org

rnrs symool

tabte,s

use the LOMTM

commard

so rhev

won r have

Lo

worry

abour

ir.

{Only

rhe label

ir"elfcoLlrts,

nor rhe

number

ofiimes ir aooears

rn lhe program.r

Alloc"ring

memory

can be

a confusing

rask for

rhe beginner.

OrJy

rwo insrruc

I'ons

iLOMI_

Il and

=)

JJe

used.

bur if they

are miiused you

ian crash

the

sy"rpm.and

lose your.work..

fonunarely.

it

yoLr

resrricr

your"elfto

small

pro_

gram"

inirially you

ll

havp

plpnry

ofempry

memory

spa,i and

tewer atJocaiion

The

-

directive

will

be followed

by

your

sour.e

proeram.

The

solDce

Droerall

is

composed

ot strlempnrs.

The

sraremenrs

muit

be writren

.ccord'i"j," .

rigorous

fbrmar.

The

rules tor wriring

slaremenrs

are

given

in

rhe nexr

s;tion.

1 2 ... 12 13 14 15 16 17 18 19 20 21 22 ... 91 92

Commentaires sur ces manuels

Pas de commentaire