Chapter
2.
Assembly
language
Concepts
2-10
The following instruction operand symbols arc also reserved:
Symbol
$
A
B
C
D
E
H
L
SP
PSW
M
Meaning
Location counter reference
Accumulator register
Register B or register pair
Band
C
Register C
Register D or register pair D and E
Register E
Register H or register pair
Hand
L
Register L
Stack pointer register
STACK
MEMORY
Program status word (Contents
of
A and status flags)
Memory reference code using address
in
Hand
L
Special relocatability feature
Special relocatability feature
NOTE
The STACK Jnd MEMORY symbols arc fully discussed
in
Chapter 4.
User-defined symbols arc symbols you create to reference instruction and data addresses. These symbols arc
defined when they appear
in
the label field
(If
an
instruction or
in
the name field of EQU, SET, or MACRO
directives
(see
Chapters 4 and 5).
Assembler·generated
~ymbols
arc created
by
the assembler to replace usel'-defined symbols whose scope
is
limited
to a macro definition.
Global and
Limited
Symbols
Most symbols arc global. This means that they have meaning thl"Oughout your program. Assume, for example,
that you assign the symbolic name
RTN
to a routine. You may then code a jump or a call to
RTN
from any
point
in
your
program. If you assign the symbolic name
RTN
to a second routine,
an
error results since you
have given multiple definitions to the same name.
Certain
symbol~
have meaning only within a macro definition or within a call to that macro; these symbols are
'local' to the macro. Macros require local
~ymbols
because the same macro may
be
used many times
in
the
program. If the symbolic
name~
within
mJcro~
were global, each
use
of the macro (except the first) would cause
multiple definitions for those symbolic names.
See
Chapter 5 for additional information ab,)ut macros.
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