8086 Questions

1)8086 microprocessor can address how many memory location?

20 power of 2 18 power of 2 32 power of 2 8 power of 2

2) Which of the flags is not regarded as control flag?

Trap flag Sign flag Interrupt flag Direction flag

3) An instruction which takes 4 clock cycles, then how many seconds it will take to execute?

0.4µs 0.8µs 1.6 µs 8µs

4) DAS and DAA instruction uses which of the following flag ….

parity flag control flag Auxiliary flag conditional flag

5) On 8086 processor chip which pin is labeled as CLK

22 18 19 20

6) When MN/MX is asserted low then 8086 is in which mode

minimum neutral zero maximum

7) Which of the following is an illegal instruction?

(a) MoV Ax, 30000 (b) iNc Al, 1 (c) aNd bx, bx (d) add ax, 30

8) Given that the subprogram putc displays the character in al, the effect of the following

instructions: mov al, ‘a’

add al, 2

call putc

is to (a) display 2 (b) display c (c) display a (d) display a blank

9) Given that the bl register contains ‘B’, the effect of the following instruction

or bl, 0010 0000

is to (a) clear bl (b) store ‘b’ in bl (c) store 0010 0000 in bl (d) leave bl unchanged

10) Which of the following is an illegal 8086 instruction…?

(a) ret 2 (b) push al (c) aDd bx, 25000 (d) and ax, dx

11) The net effect of calling the following subprogram in terms of program behaviour:

Subprog: push ax

add ax, 10

ret

is to (a) leave ax unchanged (b) add 10 to ax (c) cause the program to behave in an unpredictable manner (d) do nothing

12) An interrupt instruction

(a) Causes an unconditional transfer of control

(b) Causes a conditional transfer of Control

(c) Modifies the status register

(d) Is an I/O instruction

13) When a program is translated by the MASM assembler, the machine code is stored in a file with the extension………..

(a) .lis

(b) .obj

(c) .exe

(d) .out

14) The effect of the following instructions…

push ax

add ax, 4

pop bx

mov cx, ax

push bx

pop ax

on the ax register is

(a) leave it with its original value (b) add 4 to it (c) clear it (d) double it

15) To copy the hexadecimal number A to the bh register you write

(a) mov 0bh, ah (b) mov bh, 0ah (c) mov bh, ah (d) mov bh, [ah]

16) The word size of an 8086 processor is

(a) 8 bits (b) 16 bits (c) 32 bits (d) 64 bits

17) Pipelining improves CPU performance due to

(a) Reduced memory access time (b) increased clock speed

(c) The introduction of parallelism (d) additional functional units

18) Given that dl contains 'x' which of the following will cause 'x' to be displayed:

(a) mov ah, 1h (b) mov ah, 2h (c) mov ah, 2h (d) mov ah, 0h

int 21h int 20h int 21h int 21h

19) Which of the following will terminate a program and return to MS-DOS:

(a) mov ax, 4c00h (b) mov ax, 4c00h (c) mov dx, 4c00h (d) mov ax, 9h

int 20h int 21h int 21h int 22h

20)if AL=10000110, BH=01010111 , consider the instruction

SUB AL, BH

DAS

The output is ..

(a)29BCD (b) 39BCD (c)19BCD (d)28BCD

21) Which of the following is not part of the processor?

(a) The ALU (b) the CU (c) the registers (d) the system bus

22) Which of the following is not an MASM directive

(a) .stack (b) db (c) .model (d) call

23) The MOV reg, reg instruction requires how many clock cycles to execute?

(a) 2clock cycles (b) 4 clock cycles (c) 1 clock cycles (d) 16 clock cycles

24) The program counter

(a) Stores the address of the instruction that is currently being executed

(b) Stores the next instruction to be executed

(c) Stores the address of the next instruction to be executed

(d) Stores the instruction that is being currently executed.

25) Write a small code snippet to find whether a number is a power of 2 or not?