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Assembly Language Fundamentals
Symbol
Oper_l
Oper_2
P
Pa
R
R4
R5
R6
R7
Result
Se
Utlcount
Utlend
Utltemps
Description
} Arithmetic utility operand address registers
Program counter
Peripheral address register
Return stack pointer
I/O registers
Arithmetic utility result address register
Shift-extend register
} Reserved symbols for writing utilities
The meaning of each of these locations is discussed in other chapters. The absolute locations of
the registers can be found in Chapter 2. A description of the function of the accumulators and
pointers can be found in Chapter 3 as part of the discussion on machine instructions. A
discussion of the I/O registers and symbols can be found in Chapter 7. The arithmetic registers
are discussed in Chapter 5.
Using a pre-defined symbol in a machine instruction is the same as using its address. For
example -
means simply that register A will be loaded with the contents of register B. The same effect
could have been achieved with -
except that the symbolic form makes it more obvious what is intended by the operation. This is
true with most symbols.
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