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(COMP180)quiz01S_3.pdf
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COMP180: Computer Organization
Spring 2001, Lecture Section 1, Dit-Yan Yeung

Quiz #3
9 April 2001 Name: __________________________ Student ID: __________________ Lab: _________________ Answer all questions in the space provided. Time allowed: 20 minutes
1. For each of the following statements, write down true if it is true and false otherwise.
(a)
Twos complement is not used in the IEEE 754 floating-point representation for representing signed integers. Ans: _____

(b)
The equation dividend = quotient divisor + remainder holds for both signed and unsigned integers. Ans: _____

(c)
In a floating-point representation, overflow/underflow occurs if the significand field is not large enough to hold the value. Ans: _____

(d)
Immediate addressing is an addressing mode for loading a constant value from memory as an operand. Ans: _____

(e)
The following x86 assembly code iterates 10 times before exiting from the loop.


Again: mov cx, 10 loop Again Ans: _____
(f)
Real mode addressing is available on both 16-bit and 32-bit x86 architectures. Ans: _____

(g)
mov ax, 80000 is a valid x86 assembly instruction. Ans: _____

(h)
mov al, bx is a valid x86 assembly instruction. Ans: _____

(i)
mov cx, bx is a valid x86 assembly instruction. Ans: _____

(j)
mov 18, ax is a valid x86 assembly instruction. Ans: _____


2.
Using the integer multiplication algorithm discussed in class, show all the steps involved when two 2-bit binary numbers 11 (multiplicand) and 10 (multiplier) are multiplied to obtain the product. You can show the steps by completing the table below.

3.
Consider the following x86 assembly code, where A, B, C, D and E refer to the memory locations of five variables in the corresponding high-level language assignment statement:


Iteration Multiplicand Product Remark


1

mov eax, B
cmp eax, C
mov bl, 0
jle N1
mov bl, 1

N1: mov eax, D
cmp eax, E
mov bh, 0
jne N2
mov bh, 1

N2: or bl, bh
mov A, bl

Give a C/C++ assignment statement that corresponds to the assembly code. The statement evaluates an expression (on the right-hand side) and assigns its value to variable A.
4. Give four different methods to clear register ax (i.e., set ax to 0). Each method should use only one x86 assembly language instruction.
(a)
__________________________________________

(b)
__________________________________________

(c)
__________________________________________

(d)
__________________________________________


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