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FCVAC/IAS2123/AUG16
MIDTERM EXAMINATION
AUGUST 2016 SEMESTER EXAMINATION
ACADEMIC SESSION 2015
SUBJECT
SUBJECT CODE
DURATION
FACULTY
: COMPUTER ORGANIZATION
COMPUTER ORGANIZATION ARCHITECTURE
: IAS2123/IID2163
: 2 HOURS
: COMPUTER SCIENCE AND INFORMATION
TECHNOLOGY
INSTRUCTION TO CANDIDATES
Answer all questions.
Student Name
Matric No
Program
Total Marks
ANSWER SCHEME MID TERM
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FCVAC/IAS2123/AUG16
SECTION A (15 MARKS)
Answer ALL questions. For each question choose the best answer.
1.
Which of the following will be used by a computer to execute all programs
written on it?
A.
Active language
B.
System language
C.
Machine language
D.
Interpreted language
2.
Which utility program reads an assembly language source file and produces an
object file?
A.
Linker
B.
Loader
C.
Compiler
D.
Assembler
3.
A device driver would ordinarily be written in which language?
A.
machine language
B.
assembly language
C.
an application-oriented language
D.
a platform-independent language, such as Java
4.
Integer range of American Standard Code for Information Interchange codes
(ASCII) is _____________.
A.
-128 to +127
B.
0 to 127
C.
0 to 270
D.
0 to 65,535
5.
Which of the following is valid identifier?
A.
AB@62_$
B.
7Val2
C.
#answer
D.
Number-4
6.
The ____________ is set when the result of an operation generates an unsigned
value that is out of range (too big or too small for the destination operand).
A.
Carry flag
B.
Overflow flag
C.
Sign Flag
D.
Auxiliary Flag
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7.
Which directive identifies the part of a program containing instructions?
A.
DATA
B.
CODE
C.
STACK
D.
PROG
8.
A program is considered portable if it ____________.
A.
can be rewritten in a different programming language without losing its
meaning
B.
can be quickly copied from conventional random access memory (RAM)
into high-speed RAM
C.
can be executed on multiple platforms
D.
can be executed on single platforms
9.
The three most basic operators in Boolean algebra are _______________.
A.
AND,
B.
OR
C.
NOT
D.
XNOT
10.
Which of the following are valid data definition statements that create an array of
unsigned bytes containing decimal 10, 20, and 30, named myArray.
A.
myArray BYTE 10, 20, 30
B.
BYTE myArray 10, 20, 30
C.
BYTE myArray[3]: 10, 20,30
D.
myArray BYTE DUP (3) 10,20,30
11.
Basic program execution registers for 32-bit is/are __________.
I.
AX
II.
BX
III.
EAX
IV.
EBX
A.
B.
C.
D.
12.
I AND II
I and III
II and III
III and IV
In a statement mov EAX,10000h, identify which of the following operand is
belong to EAX?
A.
source
B.
identifier
C.
instruction
D.
destination
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13.
The following method must be used in computer system to represented negative
integer numbers in binary format.
A.
Two’s complement
B.
Digital complement
C.
Hexadecimal complement
D.
Positive to negative complement
14.
Which of the following are correct about three primary steps of the instruction
execution cycle, in sequential order?
A.
Decode, Fetch, Execute
B.
Fetch, Decode, Execute
C.
Fetch, Decode, Memory Write
D.
Fetch, Memory Read, Execute
PART B (40 MARKS)
Answer ALL questions.
Question 1 (20 marks)
a)
Draw a combinatorial circuits based on Boolean expression given.
((( B  C )  B)  (A  C ))
(8 marks)
a)
Change manually CFE + 01100111 into decimal.
(4 marks)
CFE to decimal
= 3326
01100111 to decimal = 103
3326 + 103 = 3429
c)
Form the 8-bit two's complement for 11110000.
(4 marks)
Starting value
Reverse bits
Add 1
11110000
00001111
1
00010000
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d)
Translate signed decimal numbers of -78 to binary.
(4 marks)
Binary representation of unsigned 78 is 01001110
Starting value
Reverse bits
Add 1
01001110
10110001
1
10110010
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Question 2 (20 marks)
a)
Distinguish and elaborate function for three major components of CPU
(Central Processing Unit).
 ALU (arithmetic logic unit)
◦ Performs calculations and comparisons (data changed)
 CU (control unit): performs fetch/execute cycle
◦ Functions:
 Moves data to and from CPU registers and other hardware
components (no change in data)
 Accesses program instructions and issues commands to the
ALU
 Registers
◦ Scratchpad for currently executing program
◦ Holds data needed quickly or frequently
◦ Stores information about status of CPU and currently
executing program
◦ Address of next program instruction
◦ Signals from external devices
(15 marks; 5 each)
b)
Describe the function for the following instruction mnemonics. Give one
examples for each instruction.

INC = Add 1 from destination operand; inc ebx

NEG = Reverses the sign of an operand. Operand can be a
register or memory operand. ; dec ecx
(5 marks; 2.5 each)
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Question 3 (20 marks)
Use the following variable definition for the remaining questions in this section:
.data
MyByte SBYTE -4,-2,3,1
MyWord WORD 1000h,2000h,3000h,4000h
a)
For the following statements, state whether or not the instruction is valid.
Give comment to describe the reason why the instruction become valid or
invalid.
i)
b)
mov ax, MyByte = invalid ; ax for 16 bits-MyByte is 8 bits
(4 marks)
ii)
mov ax,MyWord = valid ; ax for 16 bits-Myword is 16 bits
(4 marks)
What will be the value of the destination operand after each of the
following instructions executes in sequence? Write appropriate comment
to explain the operation executed by the instruction.
i)
mov ax, MyWord
; Comment : mov MyWord to ax (16 bits)
; ax =1000h
(4 marks)
ii)
mov ax,[MyWord + 2]
; Comment: mov Myword+2 to ax (16 bits)
; ax =2000h
(4 marks)
iii)
add ax, [MyWord + 2]
; Comment:Add value in ax(2000h) with MyWord + 2(2000h)
; ax =4000h
(4 marks)
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Question 4 (10 marks)
a)
For the following statements, state either the instructions are valid or
invalid and state the reasons:
i)
ii)
xchg var1,var2
xchg var1,bx
error: two memory operands
; exchange mem, reg
(4 marks)
b)
State the values of the destination operand after the following instructions
are executed in sequence. State the comments to explain the operations
executed by the instructions as well.
.data
arrayW WORD 6578h,4456h,3245h
arrayD DWORD 1,2,3,4
.code
viii)
viiii)
x)
mov ax,[arrayW+2]
mov ax,[arrayW+4]
mov eax,[arrayD+4]
; AX = 4456h
; AX = 3245h
; EAX = 00000002h
(6 marks)
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PART D (30 MARKS)
Answer ALL questions
Question 1
a)
Trace the error for the following assembly program. Rewrite and underline the
correct statement.
TITLE mulhexa, Version 1
(mulhexa.asm)
This program adds 32-bit integers
and stores the sum in a variable.
Last update: 30 August 2008
INCLUDE Irvine16.inc
.code
num1 DWORD 32h
num2 BYTE
finalnum WORD
1Dh
.code
main PROC
mov eax, num1
mul ebx, num2
mov finalnum, eax
DumpRegs
exit
ENDP
END
b)
; start with 32h
; mul 1Dh
; store the result
; display the registers
Trace the output for the following program.
TITLE Add and Subtract, Version 2
(AddSubbinary.asm)
; This program adds and subtracts 32-bit integers
; and stores the sum in a variable.
; Last update: 06/01/2006
INCLUDE Irvine32.inc
.data
val1 dword 100b
val2 dword 100b
val3 dword 20000h
val4
dword 200h
finalVal dword ?
.code
main PROC
mov
add
sub
add
mov
call
exit
main ENDP
END main
eax,val1
eax,val2
eax,val3
eax,val4
finalVal,eax
DumpRegs
; start with 1011b
; add 0001b
; subtract 20000h
; store the result (30000h)
; display the registers
(15 marks)
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ANSWERS
Trace the error for the following assembly program. Rewrite and underline the correct
statement.
; TITLE mul hexa, Version 1
(mulhexa.asm)
; This program adds 32-bit integers
; and stores the sum in a variable.
; Last update: 30 August 2008
INCLUDE Irvine32.inc
.data
num1 DWORD 32h
num2 DWORD 1Dh
finalnum dWORD ?
.code
main PROC
mov eax, num1
mov ebx, num2
mul ebx,
mov finalnum, eax
Call DumpRegs
exit
main ENDP
END main
; start with 32h
; mul 1Dh
; store the result
; display the registers
(10 marks; 0.5 each)
b)
Trace the output for the following program.
(5 marks)
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Question 2
Write a complete program using MASM Assembly Language 32-bit integers with
different registers. Insert the call DumpRegs statement to display the registers and flags.
Apply the following arithmetic expression and data given.
answer = (-val2 + val3) - val1*20d +1 +1 +1 - 1
Use the following data:
val1 = 150h
val2 = Ah
val3 = 26d
(15 marks)
ANSWER
;EAX = (-val2 + val3) * val1
INCLUDE Irvine32.inc
.data
val1 DWORD 150h
val2 DWORD 0Ah
val3 DWORD 26d
answer DWORD ?
.code
main PROC
mov ebx,val2
mov ecx,val3
neg ebx
add ebx,ecx
mov eax,val1
mul ebx
add eax,20d
mov answer,eax
call DumpRegs
;ebx = Ah
;ecx = 26d = 1Ah
;ebx = -Ah =FFFFFFF6h
;ebx = -Ah+1Ah =10
;eax = 150h
;ebx =10*150
;eax = 1500h
;display the registers
exit
main ENDP
END main
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a)
Based on the following conditions, calculate clock cycles that required to
execute the instructions. Provide diagram.
15. In a 6-stage dual-pipelined processor, how many clock cycles are required to
execute 5 instructions? (Assume that stage 3 requires two clock cycles, and that
stage 3 has two pipelines.)
(10 marks)
Ans :
formula
=6+5
=11
=k+n
1 mark
1 mark
S3
S1
S2
1
2
I-1
I-2
I-1
3
I-3
I-2
I-1
4
I-4
I-3
I-1
I-2
5
I-5
I-4
I-3
I-2
I-1
I-5
I-3
I-4
I-2
I-1
7
I-5
I-4
I-3
I-2
I-1
8
I-5
I-4
I-3
I-2
I-5
I-4
I-3
I-5
I-4
6
9
10
u
v
S4
S5
11
Correct cycle and
stage = 1 mark
S6
Full diagram = 2
mark
I-5
S4 u & v = 1 mark
I for u = 2 marks
I for v = 2 marks
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END OF QUESTION PAPER
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