Operator`s manual

LABEL=
DIRECTIVE
WORD Dlr€ctive
The WORD
directive is the
sam€ as the DBYTE
directiv€ €xcept
that ihe value
of
th€ €xpression
i6 stored with
th€ low-order
bj,te Iirst.
For example:
10
'
=$4000
20 .woRD
ABS+$3000
When
line 20
i6 assembled
and rhe value
ofABS+g3000
i!
derermined.
as b€fore-
to
be
$5123.
923
is
pur
in
locarion
s'4000 and
$5r is
pur
in location
ga00r.
The wORD
dfective
sjmplifies some programming
since
addesses in
machine
mde are
always
given
in rhe order low
byre fotlowed
by high byre. Therefore,
the woRD
directive is u.6eful.
for example.
in consl'-uc(ing
a rabte ofaddresses.
100
LABEL
erpression
The
LABEI
-
directive iB
u.sedto
give
a value to
a
label.
Two examples
app€ar in
the-
sample program
we used
before. Stat€ments
60
and 70
give
values io ABSX
and
XXQ as folows:
ABSX=
$3744
XEQ=
*
+$60
Since rhe symbol
that is given
a value
is a tabel,
there musr
be only one space
aller the sratemenr
number.
The
expression on
the right cannoL
f,i"", uitue
greater
than rffr
(hex,.
The rdes foi wriring
and evaluaring
an expression
are
given
in Appeodix
4.
When
rhe LAaIL=
dircciive
is used
ro
give
a value
ro a labet,
the label can
be
used
in an operand.
by itselc
as in siatemenrs
30 and aO
in the sampte
Fogram.
A delined
label may
also appear
as
part
ofan
expression.
Our sampte program
ooes nor
conlarn an
example. so we
give
one
below in line
240.
60
70
100
TAB1-$3000
24O TAB2-TAB1+92O
wh€n
the program
is
assembled, TAB2.will
be giwen
the vatue
$3020.
You
should
oote thar delining
a label
in rhis wav
Eives
rhe Iabel
a soecific
address: it doe6
nor define
thaconrenrs
of rhe addiesi. rn
rhe examp)e,
ibove,
TAB1
and TAB2
might
be the location
oftra.o tabtes
that cortained
tht values of
variables
that your prcgram
r€quired.
*
=
Direcrive
100
'-
expression
we encounrered
the
'
=
direfiive
in rhe
..gening
sraned
comrnands. where
ir
is used.Lo
set rhe
srafiing location
of fue asiembled
program.
When
the
Assemr,fer
encountefs
the
'
expre$io4.
ir sets
lhe
program
counter
io the
varue
or rne €xpr€ssron.