Atari 800 Manuel de l'opérateur télécharger pdf (Page 16)

You

can find

olrr

wherF

rhis

empty memory

area is

by ryping

SrZr

mffini.

I hree

hexade.rmaL

number" will

be displayed.

likF so:

SIZEffi

0700

0880 5c1F

NDIT

The tust

number

(0700

in this example)

is the

address ofihe

bottom of usable

RAM,

th€ point

labeled

"A"

on ih€

m€mory map. The

second

number is the

addrcss ofthe

top of th€

edit text bufer,

Iabeled

.r8,,

on the memory

map. The

third number

is ihe address

ofthe top

of empty memort,

labeled-,,C,,

;n the

memory map.

The difference

between

the second

and third rumbers

(how

good

ar€

you

at hexadecimal

subtraction?)

is the arnount

of€mDtv memoru.

you

can use the SIZE

command

any time

you

d€sire to know

h-ow much

lmpty

memory

remam6.

Liberally

estimat€ ihe

amouni of

memory

yorr

object

pm$am

wi[

require,

then subtract

that amount

from ihe

third numb"..

'ror

i*t.i i""u.a"...

.ir.-i

the rpsulr

down. for example.

ifyou

rhoughl

rhar

your

objen

code mighr

require 1.5K, you'd

subtract

2K from

g5C1F

to

g€t

$541F

and then for

simptclty

(and

additional

insurance) you

would

round atl

the way down

to

$5004.

yo;

would

therefore

store your

object

cod€ at

g5OOo,

confident that

it

would

not

encroach on

the display memory.

More

conservaiiwe

estimates and greater

carc

would

be necessary

if m€mory

werc in short

supply.

Having

decided

lo ilore rhe

obtect

program

slarrinq ar

ad&ess

$5000. vour nerr

rask is

ro declare

this to rhe compurer.

rh;s is

done-wirt

.-

direcrive."The

velv

firsr starement

ofrhe

source

code would read:

10

{

-$5000

This

direcr ive

rells rhc Assembler

ro pul

all subsequenr

object code inro

memory

starting

ar address

$5000. Alhough

ir is

nor abdlurely

neces"ary. ;r

i. always

wise praciice

to make

the

*=

directiwe

the v€ry

jirst

line oi

your

source

program.

You

have

two other str

You

havF

l$o olher srralegies

for

dllocaring memory

sprcc tor

vour

obiecl

program.

l he

firsr and simplest

srraregy

is ro-placeyouiobFcr

code 6n

paeeo

or

program.

I he lirsr

and simplest

srrareqy

is ro

place

yourobjFcl

code on Daee t oI

memory.

The 256

locarion.

on

page

o-6ave

bi,en sir

a.ide for you.

u"J. riyour

memory.

rnez5b

tocatron!

on

page

rj

have bcen setasidefbryour

ure. Ifyour

objecr

-program

and its drra wil

Jl fir inro

256 byres.

rhen

you

can pur

ir iher.

put

it there

wiih

the directive:

10

r

=$0600

This

is a good

safe way

to sra

when you

are !rill tearninq

assembty languase

programming

and are wriring

only

very

shorr

proeramsi

as

your proE"raris

grow

larger, you will

wanr

ro move

rhem offpdgi

6 ;nd use

pag;

6 io; d;

and

t he

second srrdlegy

is 10 bump

rhe edir rexr

butTpr

{your

source program)

ut)-

waro

rn memory.

leavrng some

emply memory

spar e

betow ir.

you

can rhen

prace your

oDJecl codc into

this empry

space. FigL're

3 shows

rhe adjuslmFnl

of

rne

memory

map.

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