COS2621 ASSIGNMENT 1 SOLUTIONS 2022

COS2621 ASSIGNMENT 1 SOLUTIONS 2022

QUESTION 1

(a) The following table reflects the memory contents of a part of memory in a oneaddress machine
with an accumulator




What values do the following instructions load into the accumulator?

LOAD IMMEDIATE 20

LOAD IMMEDIATE 20: Immediate addressing. The value to be used forms part of the

instruction. In this instance, the value 20 will be loaded into the accumulator.

LOAD DIRECT 20

LOAD DIRECT 20: Direct addressing. The instruction contains the address where the value

is to found. Address 20 contains the value 30, thus the value 30 will be loaded into the

accumulator.

LOAD INDIRECT 20

LOAD INDIRECT 20: Indirect addressing. The instruction contains the address where the

address of the value to be used, is to be found. Address 20 contains the address of the value

to be used, ie address 30. Address 30 contains 40, thus the value 40 will be loaded into the

accumulator.


(b) Give examples of Intel x86 instructions in which the following addressing modes are used:

Immediate addressing : Immediate addressing mov ax,23



Direct addressing : Direct addressing mov ax,[a]

, Stack addressing : Stack addressing push ax (pop ax)



Indexed addressing : Indexed addressing mov ax,[si] (mov [di],ax)



Base-addressing: Base‐addressing mov ax,[bp] (mov ax,[bx])



Register indirect addressing: Register indirect addressing mov ax,[bx]



OR




QUESTION 2

Question 2 [11]

(a) Briefly discuss the concepts of