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SET
Set a Value
The SET directive, like EQU, enables the user to define a
symbol by assigning to it the attributes of the expression in
the argument field.
SET has the form
L._a-:-b_e~I
__
+ ___
Comm'~_1
Argument
--labe I
SET
C
exp
where "label" and "exp" are the same as described for
EQU.
The SET directive differs from the EQU directive in that
any symbol defined by a SET may be redefined later by
means of a subsequent SET.
This directive is particularly
useful in writing procedures (see Chapter 7).
If
a symbol defined via a SET directive is to be redefined
but the user writes an EQU directive instead of a new SET,
Extended Symbol produces an error notification and retains
the earlier definition. This same condition holds true for
a variable defined by an EQU and later redefined by a SET.
Example 27. SET Directive
A
EQU
X'FF'
M
SET
A
M is set to the hexadecimal
value FF.
S
SET
M
Thus, S:cc M, i.e., X'FF'
M
SET
263
Redefines symbol M.
S
EQU
M
Error; does not define symbol S
SOCW
Suppress Object Control Words
The SOCW directive causes Extended Symbol to omit all
loader control information in the binary output that it pro-
duces durin!] an assembly.
This directive has the form
label
command
argument
SOCW
When Extended Symbol encounters the SOCW directive, it
sets the location counters to absolute zero, processes the
program as an absolute section, and ignores any subsequent
IDNT or LBL directive. An eriOr flag is given if those
directives that require control byte generation are used
(DEF, REF, or SREF)'
An error is also given if those direc-
tives that have no meaning for a program being assemblpd
with SOCW are used (COMMON and GSECT), if an
illegal ob ject language feature is subsequently required
(such as the occurrence of a procedure -Ioca I forward refer-
ence), or if the SOCW directive is used subsequent to the
generation of any object code in the program.
38
Extended Symbol Directives
Use of the BOUND, LOC, ORG, and RES directives is
allowed, although this is a highly questionable practice
(i. e., no code is generated for these directives, but the
location counters are modified as directed).
Once the SOCW directive is invoked, it remains in effect
during the assembly of the entire program.
Norma lIy, contro I words are produced to convey to the
loader info,mation concerning program relocation, exter-
nally defined and/or referenced symbols, etc.
In special
cases, such as writing bootstrap loaders and special diag-
nostic programs, the programmer does not want the control
words produced; he needs only the continuous string of bits
that result from an assembly of statements. The SOCW
directive enables the programmer to suppress the output of
these control words.
When SOCW is specified, it is recommended that it be the
first statement in the program, or at least precede the first
generative statement.
SPACE
Insert Blank Lines
The SPACE directive causes b lank lines to be inserted in
the assembly listing; its form is
Label
Command
Argument
SPACE
n
where
n
is an evaluatable absolute expression (no literal,
external, or forward references) designating the
number of b lank lines to be inserted.
If
the
va lue of n is negative or zero, the directive is
ignored.
If the value of n equals or exceeds the
number of lines remaining to be output on the
current page, then a SPACE directive has the same
effect as a PAGE directive.
A label field entry is ignored by the assembler unless it is
the target of a GOTO search.
SREF
Secondary Externa I References
The SREF directive is similar to REF and has the form
Command
Ar ument
SREF
symbol
1
~,
symbol
2
, •.. , symbol
n
)
where each symbol has the same meaning as described for
REF.
A label field entry is ignored by the assemb ler.
SREF differs from REF in that REF causes the loader to
load programs whose labels it references, whereas SREF
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