8086 interview questions

  1. What are the flags in 8086? - In 8086 Carry flag, Parity flag, Auxiliary carry flag, Zero flag, Overflow flag, Trace flag, Interrupt flag, Direction flag, and Sign flag.

  2. What are the various interrupts in 8086? - Maskable interrupts, Non-Maskable interrupts.
  3. What is meant by Maskable interrupts? - An interrupt that can be turned off by the programmer is known as Maskable interrupt.
  4. What is Non-Maskable interrupts? - An interrupt which can be never be turned off (ie.disabled) is known as Non-Maskable interrupt.
  5. Which interrupts are generally used for critical events? - Non-Maskable interrupts are used in critical events. Such as Power failure, Emergency, Shut off etc.,
  6. Give examples for Maskable interrupts? - RST 7.5, RST6.5, RST5.5 are Maskable interrupts
  7. Give example for Non-Maskable interrupts? - Trap is known as Non-Maskable interrupts, which is used in emergency condition.
  8. What is the Maximum clock frequency in 8086? - 5 Mhz is the Maximum clock frequency in 8086.
  9. What are the various segment registers in 8086? - Code, Data, Stack, Extra Segment registers in 8086.
  10. Which Stack is used in 8086? - FIFO (First In First Out) stack is used in 8086.In this type of Stack the first stored information is retrieved first.
  11. What are the address lines for the software interrupts? -









    RST 0 0000 H
    RST1 0008 H
    RST2 0010 H
    RST3 0018 H
    RST4 0020 H
    RST5 0028 H
    RST6 0030 H
    RST7 0038 H
  12. What is SIM and RIM instructions? - SIM is Set Interrupt Mask. Used to mask the hardware interrupts. RIM is Read Interrupt Mask. Used to check whether the interrupt is Masked or not.
  13. Which is the tool used to connect the user and the computer? - Interpreter is the tool used to connect the user and the tool.
  14. What is the position of the Stack Pointer after the PUSH instruction? - The address line is 02 less than the earlier value.
  15. What is the position of the Stack Pointer after the POP instruction? - The address line is 02 greater than the earlier value.
  16. Logic calculations are done in which type of registers? - Accumulator is the register in which Arithmetic and Logic calculations are done.
  17. What are the different functional units in 8086? - Bus Interface Unit and Execution unit, are the two different functional units in 8086.
  18. Give examples for Micro controller? - Z80, Intel MSC51 &96, Motorola are the best examples of Microcontroller.
  19. What is meant by cross-compiler? - A program runs on one machine and executes on another is called as cross-compiler.
  20. What are the address lines for the hardware interrupts? -





    RST 7.5 003C H
    RST 6.5 0034 H
    RST 5.5 002C H
    TRAP 0024 H
  21. Which Segment is used to store interrupt and subroutine return address registers? - Stack Segment in segment register is used to store interrupt and subroutine return address registers.
  22. Which Flags can be set or reset by the programmer and also used to control the operation of the processor? - Trace Flag, Interrupt Flag, Direction Flag.
  23. What does EU do? - Execution Unit receives program instruction codes and data from BIU, executes these instructions and store the result in general registers.
  24. Which microprocessor accepts the program written for 8086 without any changes? - 8088 is that processor.
  25. What is the difference between 8086 and 8088? - The BIU in 8088 is 8-bit data bus & 16- bit in 8086.Instruction queue is 4 byte long in 8088and 6 byte in 8086.
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29 Comments on 8086 interview questions

  1. mallikarjuna
    Posted 4/5/2005 at 10:32 pm | Permalink

    in 8086

    itd not fifo for stack its lifo

  2. barkat
    Posted 5/23/2005 at 1:47 pm | Permalink

    its FIFO can never be implemented on a stack!!:P if its a fifo stack it is a queue not a stack
    a stack must always be first in last out… :)

  3. Sahebbb
    Posted 6/24/2005 at 3:45 am | Permalink

    why do we call microprocessor as MICRO processor and why not only Processor
    ?

  4. Posted 6/25/2005 at 1:54 am | Permalink

    A microprocessor is a processor in specific packaging, with all components on board. Most of the modern-day processors are sold as microprocessors, meaning that CPU, cache, etc. come in one package.

  5. Sudeep
    Posted 8/17/2005 at 2:06 pm | Permalink

    The T flag expansion is TRAP flag and not TRACE flag.It is used for single stepping in the code.

  6. steven
    Posted 1/14/2006 at 3:12 am | Permalink

    18. Z80 is not a microcontroller but an 8-bit microprocessor.

  7. elumalai
    Posted 1/27/2006 at 10:30 am | Permalink

    #8.The maximum clock frequency of 8086 is upto 10MHz.

  8. garidaa
    Posted 6/9/2006 at 4:40 am | Permalink

    connect rst5.5 between rst6.5

  9. BHUVANESWARI
    Posted 9/22/2006 at 6:54 am | Permalink

    why there r 2 gnd pins in 8086 microprocessor?

  10. Posted 9/28/2006 at 11:50 pm | Permalink

    What is use of RST5.5 ,RST6.5,RST7.5 in microprocessor?

  11. Posted 9/28/2006 at 11:53 pm | Permalink

    what is mean by VSS pin in 8085?

  12. Thomas
    Posted 10/27/2006 at 4:18 am | Permalink

    What is the requrement of two ground pins for 8086 ? I am eagerly looking for the answer

  13. shailesh
    Posted 11/20/2006 at 5:38 am | Permalink

    Perhapes,
    TO maintain the packging symmety of 8086 which is 40 pin two GND pins are there. there is no specific use as per the interfacing with other periwares are concern.

  14. sandeep
    Posted 11/30/2006 at 6:54 am | Permalink

    I know some software interrupts like

    mov ah,4cH
    mov ah,09H
    mov ah,3cH

    etc………..

    I wanted ALL SOFTWARE INTERRUPTS for
    intel 8086 microprocessor,since we have it for Exams.
    I hope someone will help me

    Thanks……………………..

  15. Nirmal Raj Chataut
    Posted 12/24/2006 at 2:06 am | Permalink

    What are the main difference the 8086 and 8088 microprocessor?

  16. Nirmal Raj Chataut
    Posted 12/24/2006 at 2:07 am | Permalink

    How can we compare 8088 and 8086?

  17. richard
    Posted 1/26/2007 at 3:34 am | Permalink

    what will be the ouput if
    mov ax,09h
    mov bx,5h
    add ax,bx

  18. krithika
    Posted 2/12/2007 at 3:17 am | Permalink

    Non Maskable Interrupt is a…..

    a) NMI
    b) Software interrupts
    c) Hardware interrupts
    d) Software and hardware interrupt

  19. aleexain
    Posted 2/14/2007 at 5:36 am | Permalink

    NMI is hardware interrupt.

    @richard
    14h

    @vinod
    to supply(i.e +5V)

    What is use of RST5.5 ,RST6.5,RST7.5 in microprocessor?

    RST5.5 is a maskable interrupt. When this interrupt is received the processor saves the contents of the PC register into stack and branches to 2Ch (hexadecimal) address.

    RST6.5 is a maskable interrupt. When this interrupt is received the processor saves the contents of the PC register into stack and branches to 34h (hexadecimal) address.

    RST7.5 is a maskable interrupt. When this interrupt is received the processor saves the contents of the PC register into stack and branches to 3Ch (hexadecimal) address.

  20. Dayanand Kumbhar
    Posted 3/24/2007 at 4:35 pm | Permalink

    Q. What will happen when a number is divided by 0 in 8086 microprocessor?

  21. A.Sri Chand
    Posted 3/30/2007 at 3:06 am | Permalink

    what is the clock frequency of HPC 16 bit micro processor

  22. Rishi
    Posted 4/26/2007 at 1:39 am | Permalink

    @aleexain
    Vss is usually the most negative point.
    This might help..http://encyclobeamia.solarbotics.net/articles/vxx.html

    @Dayanand Kumbhar
    When a numebr is divided by 0, 8086 consider it as divide by zero error. It arise in case like
    DIV BX ; this divies DX-AX by BX. If the quotient is too large to accomodate in AX
    or
    DIV BL; this divided AX by BL. If teh quotient is too large to accomodate in Al
    In both the cases, it is considered to be divide by zero error.
    INT 00H, i.e. interrupt type 0 is called for the divide by zero error. M not excatly sure what goes in AX/AL in that case, but i think that value remains unchanged.
    @

  23. ankita
    Posted 4/27/2007 at 2:22 am | Permalink

    8088 is a 8-bit microprocessor while 8086 is 16 bit.
    8088 has instruction queue of 4 bytes whereas 8086 has a 6 byte queue

  24. sarala patil
    Posted 5/22/2007 at 5:12 am | Permalink

    Hi,
    1>What is the actual difference between macro and procedure?
    2)What is the meaning of INT 21 interrupt

  25. Ammad ud Din
    Posted 7/24/2007 at 11:50 pm | Permalink

    Why we named them 8086,8088,80286 and etc

  26. Snehanshu Shekhar
    Posted 8/25/2007 at 1:25 pm | Permalink

    [25].
    8086 Vs 8088:
    8086 prefetches only when atleast 2 bytes are free in queue
    8088 prefetches only when atleast 1 byte is free in queue

  27. prashanth
    Posted 9/2/2007 at 1:03 pm | Permalink

    Can anybody can find the number of bus cycles required for all instruction in 8086

  28. Ranganath
    Posted 3/23/2008 at 11:38 pm | Permalink

    1) What are Level triggered Interrupts?
    2) What are Edge triggered Interrupts?
    3) What are those Interrupts?

  29. Vlada
    Posted 4/30/2008 at 8:01 pm | Permalink

    (IP)=200H, (CS)=1000H, (DS)=0005H, (SS)=0009H, (ES)=00004H, (AX)=4H, (BX)=7H, (CX)=3H, (DX)=8H, (SP)=100H, (BP)=9H

    what will be the ouput if

    mov SI, DX
    add AX, [BX] ________
    add AL, [BP][SI] ________
    add AX, [BX+4][SI] ________

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