CSC231 Sample Midterm Questions

--D. Thiebaut (talk) 08:01, 21 October 2015 (EDT)

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Below are typical questions you might expect during the in-class CSC231 Midterm Exam

Question 1

Assume that eax, ebx, ecx, and edx all 4 contain the value 0 before the program below start. Indicate the value of each 32-bit register after each instruction has been executed.

	
	;; eax = ebx = ecx = edx = 0x00000000                                                                       

        mov     al, 3           ; eax = 0x00000003                                                                  
        mov	bx, 0x1122	; ebx = __________                                                                  
        mov	ecx,3		; ecx = __________                                                                  
        mov	ah, 5		; eax = __________                                                                  
        mov	ecx, 10		; ecx = __________                                                                  
for:	inc	edx
        loop    for
                                ; edx = __________                                                                  
				; ecx = __________

Question 2

Same as Question 1

        ;; eax = ebx = ecx = edx = 0x00000000                                                                       

	or	ax, 0xffff	; eax = __________                                                                  
        or	bl, 0xff	; ebx = __________                                                                  
        or	cx, 0xff	; ecx = __________                                                                  
        or	edx,0xffff0000	; edx = __________                                                                  
        and	ax, 0xff00	; eax = __________                                                                  
	and	bx, 0x0f	; ebx = __________

Question 3

Write a short program that displays all the numbers from 25 down to 1. We assume that _printDec and _println are available.

Question 4

Write a short program that displays all the numbers from 5 to 20.

Question 5

What is a segmentation fault?

Question 6

What is printed by the following code? Do not worry about it lacking an exit section.

        section .data
msg     db      10,10,10,"hello ",10
msg2    db      "world",10,"!"
msg3    db      0x0a

        section .text
        mov     ebx,msg
        add     byte [ebx+9],'-'-10
        mov     byte [msg3-2],' '
        mov     eax, 4
        mov     ebx, 1
	mov     ecx,msg
	mov     edx,msg3-msg
	int     0x80

Question 7

What is a big-endian processor?

Question 8

Write a program that uses only one string of characters "********" and that prints this pattern:

********
******
****
**

Question 9

The RAM containing the data section of the program below is shown here, as a collection of successive bytes. The top byte has the lowest address of the group. In other words, addresses increase as we go down the array of bytes.

Show the contents of the RAM once the array has been initialized with the variables a, b, msg and c.

 

        section    .data
a       dd         10
b       dd         0x1234
msg     db         1,2,3,4,5,6,7
c       dw         0xaa

        +--------------+
        |              |
        +--------------+
	|              |
	+--------------+
        |              |
        +--------------+
        |              |
        +--------------+
        |              |
	+--------------+
        |              |
        +--------------+
        |              |
        +--------------+
        |              |
        +--------------+
	|              |
	+--------------+
        |              |
        +--------------+
        |              |
        +--------------+
        |              |
	+--------------+
        |              |
        +--------------+
        |              |
        +--------------+
        |              |
        +--------------+
        |              |
        +--------------+
        |              |
	+--------------+
        |              |
        +--------------+
        |              |
        +--------------+

Question 10

• Convert the following hexadecimal numbers in binary

• 1
• 10
• 16

• Convert the following decimal numbers to binary

• 1
• 10
• 16

• Convert the following binary numbers to hexadecimal

• 1001
• 11001101
• 111000111000

• 'A' has ASCII code 0x41.

• What is the code for 'B'?
• What is 'A' + 0x20, in hex, in ASCII, or in decimal?