The document discusses addressing modes and instruction formats. It describes different addressing modes like immediate, direct, indirect, register, displacement and stack addressing modes. It also discusses basic operand types and provides examples of different addressing modes in x86 architecture. The document then covers instruction formats and factors that influence instruction length and allocation of bits within an instruction. It concludes with a brief introduction to assembly language and how assembly compilers translate assembly code to machine code.

1. A D D R E S S I N G M O D E S A N D
F O R M A T S
C H A P T E R 1 3 I N S T R U C T I O N S E T S

2. L I S T O F C O N T E N T S
A d d r e s s i n g
M o d e s
X
I n s t r u c t i o n
F o r m a t s
P A G E 0 2 A D D R E S S I N G M O D E S
A N D F O R M A T S
C H A P T E R 1 3 I N S T R U C T I O N S E T S
X
A s s e m b l y
L a n g u a g e

3. A D D R E S S I N G M O D E S
P A G E 0 3 A D D R E S S I N G M O D E S A N D F O R M A T S
Addressing Modes specify how to calculate
the effective memory address of an operand
by using information held in registers and/or
constants contained within a machine
instruction
It provides the means & ways to access
various operands in an assembly language
program, and is completely architecture
dependent

4.  Immediate
 Register
Memory
►Constant integer (8, 16, or 32 bits) 
►Constant value is stored within the instruction
►Name of a register is specified
►Register number is encoded within the instruction
►Reference to a location in memory
►Memory address is encoded within the instruction
►Register holds the address of a memory location
B A S I C O P E R A N D T Y P E S

5. P A G E 0 5 A D D R E S S I N G M O D E S A N D F O R M A T S
A D D R E S S I N G
M O D E S

6. I M M E D I A T E A D D R E S S I N G
O P E R A N D = A
P A G E 0 6
C H A P T E R 1 3 I N S T R U C T I O N S E T S
Advantage: no memory reference.
A D D R E S S I N G M O D E S
A N D F O R M A T S
Example: ADD 5 Add 5 to contents of accumulator
Disadvantage: size of number is restricted to size of
address field.
x86 Examples:

7. D I R E C T
A D D R E S S I N G E A = A
x86 Examples
P A G E 0 7 A D D R E S S I N G M O D E S
A N D F O R M A T S
Disadvantage: Limited address spaceDisadvantage:
Limited address space
Advantage: Single memory reference to access data
Example: ADD A Add contents of cell A to accumulator
Look in memory at address A for operand
► mov count, [var]

8. I N D I R E C T A D D R E S S I N G
E A = ( A )
► A second to get the value
P A G E 0 8 A D D R E S S I N G M O D E S
A N D F O R M A T S
x86 examples - none
Disadvantage: instruction execution requires two memory
references to fetch operand:
Example: ADD (A) Add contents of cell pointed to by
contents of A to accumulator
Advantage: for a word length of N, an address space of 2N is
now available.
Parentheses are to be interpreted as meaning contents of.
► One to get the address

9. P A G E 0 9 C H A P T E R 1 3 I N S T R U C T I O N S E T S
R E G I S T E R A D D R E S S I N G
E A = R
A D D R E S S I N G M O D E S
A N D F O R M A T S
Typically, an address field that references registers will have
from 3 to 5 bits, so that a total of from 8 to 32 general-purpose
registers can be referenced.
x86 Examples
 Disadvantage
Advantage:
► Only a small address field is needed in instruction.
► No memory references are required
► Address space is very limited.
► MOV EAX,EBX MOV CX,DX

10. R E G I S T E R A D D R E S S I N G
E A = R
P A G E 1 0
Operand is in memory cell pointed to by contents of register R.
A D D R E S S I N G M O D E S
A N D F O R M A T S
MOV AL,[BX] MOV AX,[EBX]
MOV [EDI],EAX MOV [EAX],EDX
x86 Example
Advantages: basically same for indirect addressing. Register indirect addressing
has a large address space (2N). Register indirect addressing uses one less
memory reference than indirect addressing.

11. E
Z
=
A
+
( R )
C H A P T E R 1 3 I N S T R U C T I O N S E T S
P A G E 1 1 A D D R E S S I N G M O D E S
A N D F O R M A T S
Address field holds two values:
A = base value
R = register that holds displacement
x86 Example
MOV AX, NAME[SI]
D I S P L A C E M E N T A D D R E S S I N G

12. S T A C K A D D R E S S I N G
E A = T O P O F S T A C K
P A G E 1 2
C H A P T E R 1 3 I N S T R U C T I O N S E T S
A D D R E S S I N G M O D E S
A N D F O R M A T S
Machine instructions need not include a memory reference
but implicitly operate on top of stack
Stack pointer is maintained in a register
Example:ADD Pop top two items from stack, add, place the
result on top of the stack

13. I N S T R U C T I O N F O R M A T S
T h e i n s t r u c t i o n f o r m a t i s s i m p l y a s e q u e n c e o f b i t s ( b i n a r y 0 O r 1 ) c o n t a i n e d i n a m a c h i n e
i n s t r u c t i o n t h a t d e f i n e s t h e l a y o u t o f t h e i n s t r u c t i o n . T h e m a c h i n e i n s t r u c t i o n c o n t a i n s n u m b e r
o f b i t s ( p a t t e r n o f 0 a n d 1 ) . T h e s e b i t s a r e g r o u p e d t o g e t h e r c a l l e d f i e l d s .
P A G E 1 3 A D D R E S S I N G M O D E S A N D F O R M A T S
C H A P T E R 1 3 I N S T R U C T I O N S E T S

14. Memory size
Memory organization
Bus structure
Processor complexity
Processor speed
I N S T R U C T I O N L E N G T H
P A G E 1 4 A D D R E S S I N G M O D E S
A N D F O R M A T S
Should be a multiple of the character length, which is usually 8 bits,
and of the length of fixed-point numbers
Affects, and is affected by:
Should be equal to the memory-transfer length or
one should be a multiple of the other
Most basic design issue

15. A L L O C A T I O N O F B I T S
P A G E 1 5 A D D R E S S I N G M O D E S
A N D F O R M A T S
Number of addressing modes
Number of operands
Register versus memory
Number of register sets
Address range
Address granularity

16. P A G E 0 9 C H A P T E R 1 6 I N S T R U C T I O N S E T S
V A R I A B L E - L E N G T H
I N S T R U C T I O N S
A D D R E S S I N G M O D E S
A N D F O R M A T S
Variations can be provided efficiently and compactly
Does not remove the desirability of making all of the
instruction lengths integrally related to word length
Increases the complexity of the processor
► Because the processor does not know the length of
the next instruction to be fetched a typical strategy is to
fetch a number of bytes or words equal to at least the
longest possible instruction
► Sometimes multiple instructions are fetched

17. P A G E 1 7
A
D
D
R
E
S
S
I
N
G
M
O
D
E
S
A
N
D
F
O
R
M
A
T
S
I N S T R U C T I O N
F O R M A T

18. P A G E 1 8
I N S T R U C T I O N F O R M A T
A D D R E S S I N G M O D E S
A N D F O R M A T S

19. 1 3 . 5
P A G E 1 9
A S S E M B L Y
L A N G U A G E
A D D R E S S I N G M O D E S
A N D F O R M A T S
AN ASSEMBLY LANGUAGE IS A TYPE OF LOW-LEVEL
PROGRAMMING LANGUAGE THAT IS INTENDED TO
COMMUNICATE DIRECTLY WITH A COMPUTER’S
HARDWARE..
UNLIKE MACHINE LANGUAGE, WHICH CONSISTS OF
BINARY AND HEXADECIMAL CHARACTERS, ASSEMBLY
LANGUAGES ARE DESIGNED TO BE READABLE BY
HUMANS.

20. A S S E M B L Y L A N G U A G E
L O W - L E V E L P R O G R A M M I N G
L A N G U A G E S S U C H A S A S S E M B L Y
L A N G U A G E A R E A N E C E S S A R Y B R I D G E
B E T W E E N T H E U N D E R L Y I N G
H A R D W A R E O F A C O M P U T E R A N D T H E
H I G H E R - L E V E L P R O G R A M M I N G
L A N G U A G E S — S U C H A S P Y T H O N O R
J A V A S C R I P T — I N W H I C H M O D E R N
S O F T W A R E P R O G R A M S A R E W R I T T E N .
P A G E 2 0 A D D R E S S I N G M O D E S
A N D F O R M A T S
A D D R E S S I N G M O D E S A N D F O R M A T S

21. A S S E M B L Y
C O M P I L E R
P A G E 2 1 A D D R E S S I N G M O D E S
A N D F O R M A T S
Fundamentally, the most basic instructions
executed by a computer are binary codes,
consisting of ones and zeros. Those codes
are directly translated into the “on” and “off”
states of the electricity moving through the
computer’s physical circuits. In essence,
these simple codes form the basis of
“machine language”, the most fundamental
variety of programming language.

22. T H A N K Y O U V E R Y M U C H !
A D D R E S S I N G M O D E S A N D F O R M A T S
P A G E 2 2 A D D R E S S I N G M O D E S A N D F O R M A T S