Chapter 4 Assembly Language and Cross Assembler
Syntax
ORG
expression
·
Description
This directive sets the location counter to
expression.
The subsequent code and data offsets
begin at the new offset specified by
expression.
The code or data offset is relative to the be-
ginning of the section where the directive
ORG
is defined. The attribute of a section determines
the actual value of offset, absolute or relative.
·
Example
ORG 8
mov A, 1
In this example, the statement
mov A, 1
begins at location 8 in the current section.
Syntax
PUBLIC
name1
[,name2 [,...]]
EXTERN
name1:type
[,name2:type [, ...]]
·
Description
The
PUBLIC
directive marks the variable or label specified by a name that is available to other
modules in the program. The
EXTERN
directive, on the other hand, declares an external vari-
able, label or symbol of the specified name and type. The type can be one of the four types:
BYTE, WORD
and
BIT
(these three types are for data variables), and
NEAR
(a label type and
used by call or jmp).
·
Example
PUBLIC start, setflag
EXTERN tmpbuf:byte
CODE
.SECTION
¢CODE¢
start:
mov
a, 55h
call setflag
....
setflag
proc
mov
tmpbuf, a
ret
setflag
endp
end
In this example, both the label
start
and the procedure
setflag
are declared as public vari-
ables. Programs in other sources may refer to these variables. The variable
tmpbuf
is also de-
clared as external. There should be a source file defining a byte that is named
tmpbuf
and is
declared as a public variable.
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