Digital System, Computer Organization and architecture

(1 mark each)


1)      A toggle flip-flop can be constructed using JK flip-flop by connecting the

a)      Toggle input of J and the inverted form of toggle input to ih

b)      Toggle input to J

c)      Inverted form of toggle input to K

d)     None of the above


2)      The sum of two octal numbers 12 and 17 would be in octal as

a)      21

b)      23

c)      29

d)     31


3)      The sum of two Hexadecimal numbers 23D and 9AA gives the hexadecimal number

a)      BE7

b)      BE5

c)      BF6

d)     AF7


4)      The number of select lines required for a to 1 multiplexer is

a)      1

b)      3

c)      8

d)     256


5)      Which of the following gates recognizes only words that have an odd number of 1s

a)      NAND

b)     XOR

c)      NOR

d)     None of these

6)      If even parity mechanism is being used in system using ASCII code for data transfer, incorrect receipt data byte is

a)      B5

b)     1

c)      2

d)     None of these


7)      Any combinational circuit can be implemented by using the following building block

a)      AND

b)     NAND

c)      OR

d)     None of these



8)      The number of memory location that a CPU with a 16 bit program counter can address

a)      16k

b)      64k

c)      256k

d)     32 k


9)      The following logic building block can be used to implement any combinational logic circuit

a)      Decoder

b)     Multiplexer

c)      Ex-Or gate

d)     Encoder


10) A module 20 counter can be designed using

a)      4 flip-flops

b)      20 flip-flops

c)      5 flip-flops

d)     None of these


11) A computer stores it’s data in memory

a)      Decimal form

b)      Octal form

c)      Hexadecimal form

d)     Binary form


12) The least negative valaue that the product of two 8-bit 2’s complement number can take is

a)      -214

b)     -215

c)      -216

d)     None of these


13) The simplified form of the expression AB+ABC’ is

a)      AB

b)      A(B+C)

c)      A(B+C)’

d)     None of these


14) In half subtractor borrow is obtained by (for inputs A & B)

a)      AB

b)     A’B

c)      A’B’

d)     None of these


15)  The numbers in the range -23 to +31 is represented by minimum number of bits

a)      6

b)      8

c)      7

d)     5


16) Which of the following is a unit of measurement with computer systems

a)      Byte

b)      Megabyte

c)      Kilobyte

d)     All of above


17) The number of select input lines in an 16-to-1 multiplexer is

a)      4

b)      8

c)      1

d)     None of the above


18) Code segment register is where the microprocessor looks for

a)      Stack

b)      Data

c)      Instruction

d)     Operand


19) In register addressing mode operands are looked at

a)      In cache

b)      In secondary storage

c)      In cpu

d)     In primary memory


20) BCD stands for

a)      Boolean code definition

b)      Binary coded division

c)      Binary coded decimal

d)     None of the above


21) The basic circuit of ECL supports the

a)      NAND logic

b)      NOR logic

c)      EX-OR logic

d)     OR-NOR logic


22) In a half – adder, CARRY is obtained by using

a)      OR gate

b)      NAND gate

c)      AND gate

d)     EX-NOR gate

23) If the radix point (binary point) is fixed and assumed to be to on the right of the right most digit, the representation of such number is called

a)      Fixed point

b)      Floating point

c)      Radix point

d)     None of these


24) Which of the following memory elements uses an RC circuit as its input?

a)      Unclocked D latch

b)      Level-clocked D latch

c)      Edge – triggered D flip-flop

d)     None of the above


25) The minimum hardware required to construct a 3-to-8 decoder is using

a)      Two 2-to-4 decoders

b)      Two 2-to-4 decoders and a two 1-to-2 decoders

c)      Depends upon the technology (TTL, CMOS, etc.)

d)     None of the above


26) Two 4-bit 2’s compliment numbers are added using a ripple carry adder, the range of the sum output is

a)      -128 to +127

b)      -256 to +255

c)      -512 to + 511

d)     -256 to + 256


27) In order to correct a single error, the minimum number of check bits that must be added to 4 data bits is

a)      2

b)      3

c)      4

d)     There is insufficient data to answer the question


28) Octal number system is

a)      A positional system with weights 0 to 9

b)      A positional system with weights 0 to 8

c)      A positional system with weights 0 to 7

d)     A non positional system with weights 0 to 7


29) A 4 digit BCD number can be represented with the help of

a)      10 bits

b)      8 bits

c)      12 bits

d)     16 bits


30)  A truth table of the n variables has ……………………. Minterms

a)      N2

b)      (n-1)2

c)      2n

d)     2n-1


31) Which of the following shift operations divide a signed binary number of 2

a)      Logical left shift

b)      Logical right shift

c)      Arithmetic left shift

d)     Arithmetic right shift


32) Dual of a+b.c is

a)      (a+b).(a+c)

b)      a.(b+c)

c)      a’.(b’+c’)

d)     (a’+b’).(a’+c’)


33) A combinational circuit that converts binary information from n coded inputs to a maximum of 2n unique outputs called as

a)      Encoder

b)     Decoder

c)      Multiplexer

d)     Demultiplexer


34) Decimal equivalent of the binary number 101001.1011 is

a)      41.0875

b)     41.06875

c)      416875

d)     40.0875


35) The half adder performs

a)      Decimal addition operation for 2 decimal inputs

b)     Binary addition operation for 2 binary inputs

c)      Decimal addition operation for 2 binary inputs

d)     Binary addition operation for 2 decimal inputs


36) A flip-flop circuit can be used for

a)      Counting

b)      Scaling

c)      Rectification

d)     Demodulation


37) Normally digital computers are based on

a)      AND and OR gates

b)     NAND and NOR gates

c)      Not gate

d)     None of these


38) Which one does not change the information content during movement of binary information in registers

a)      Register transfer micro-operations

b)      Arithmetic operations

c)      Logic operations

d)     None of above


39) Using Binary division, divide 1011011 by 111

a)      101.01

b)     1011

c)      011.01

d)     1101


40) The ‘T’ in the flip flop stands for ……………………..

a)      Time

b)      Transfer

c)      Toggle

d)     Trigger


(2marks each)


41) Which of the following statements is wrong ?

a)      Propagation delay is the time required for a gate to change its state.

b)      The noise immunity is the amount of noise which can be applied to the input of agate without causing the gate to change state.

c)      Fan-in of a gate is always equal to fan-out of the same gate

d)     Operating speed is the maximum frequency at which digital data can be applied to a gate.


42)   The functional capacity of SSI devices is

a)      1-11 gates

b)      12 to 99 gates

c)       100 to 10,000 gates

d)      more than 10000 gates


43)   The functional capacity of LSI devices is

a)      1-11 gates

b)      12 to 99 gates

c)       100 to 10,000 gates

d)      more than 10000 gates


44)   The functional capacity of VLSI devices is

a)      1-11 gates

b)      12 to 99 gates

c)       100 to 10,000 gates

d)      more than 10000 gates


45)   Let X and Y be the input and Z be the output of NAND gate, the value of the Z is given by :

a)      X+Y

b)      X.Y

c)       (X.Y)’

d)      X’.Y’


46)   Let X and Y be the input and Z be the output of XOR gate, the value of the Z is given by :

a)      X+Y

b)      X.Y

c)       (X.Y)’

d)      X’.Y + X.Y’


47)   The NAND can function as a NOT gate if (A.B)’=A’+B’

a)      Inputs are connected together

b)      One input is set to 0

c)       One input is set to 1

d)      Both a and c


48)   The Boolean expression (A+C) (AB’+AC) (A’C’+B) simplified to

a)      AB+A’C

b)      A’B+BC

c)       AB+BC

d)      AB’


49)   What is the minimum number of 2-input NAND gates required to implement the function

F= (x’+y’)(z+w) ?

a)      6

b)      5

c)       4

d)      3


50)   A One-to-Four demultiplexer is to be implemented using a memory. How many words of memory are required ? How many bits must each word have?

a)      4 words, 1 bit

b)      4 words, 4 bits

c)       8 words, 1 bit

d)      8 words, 4 bits


51)   Which one of the following Boolean expression represents the SUM output of a HALF-ADDER.

a)      A.B

b)      A+B

c)      A’.B’+A.B

d)     A.B’+A’.B


52)   A JK flip flop has its J input connected to logic level1 and its input to the Q output. A clock pulse is fed to its clock input. The flip – flop will now

a)      Change its state at each clock pulse

b)      go to state 1 and stay there

c)      go to state 0 and stay there

d)     retains its previous state


53) Convert x’yz’+x’y’z+x(y+z) into a product of sums.

a)      x’yz’+x’y’z+xy+xz

b)     (x’+y+z’) (x’+y’+z)(x+y) (x+z)

c)      (y’+z’)(x’+y+z)

d)     (y+z)(x+y’+z’)


54)   The main difference between JK and RS flip-flop is that

a)      JK flip-flop does not need a clock pulse.

b)      there is a feedback in JK flip-flop

c)      JK flip-flop accepts both inputs as 1

d)     JK flip-flop is acronym of Junction cathode multivibrator


55) If a clock with time period ‘T’ is used with n stage shift register , then output of the final stage will be delayed by

a)      nTsec.

b)     (n-1)T sec.

c)      n/Tsec.

d)     (2n-1)T sec.


56) Hamming codes are used to error detection and correction . If the minimum Hamming distance is m, then the number of errors correctable is

a)      equal to m

b)     less than m/2

c)      equal to 2m

d)     greater than m


57) The minterms corresponding to decimal number 15 is

a)      ABCD

b)      (ABCD)’

c)      A+B+C+D

d)     A’+B’+C’+D’


58) The resolution of D/A converter is approximately 0.4% of its full scale range. It is a

a)      8 – bit converter

b)      10 – bit converter

c)      12– bit converter

d)     16– bit converter

59) The operation which is cumulative but not associative is

a)      AND

b)      OR

c)      EX-OR

d)     NAND


60) The dual of the boolean theorm A.(B+C) = A.B + A.C is

a)      A + (B+C) = A.B + A.C

b)      A.(B+C) = (A+B) + (A+C)

c)      A+B.C = (A+B) + (A+C)

d)     None of these


(4 marks each)


61) Which of the following represent cumulative law , Associative law and Distributed law ?

I.                   A. (B.C) = (A.B).C

II.                A . (B+C) = A.B + A.C

III.             A+B = B+A

a.       I, III and II respectively

b.      II, I and III respectively

c.       III, II and I respectively

d.      III, I and II respectively


62) Match List – I with List – II and select the correct answer using the codes given below the lists:

List – I                                          List - II

A. AÅ B=0                                   1. A¹ B

B. (A+B)’ =0                                2. A=B

C. A’.B=0                                     3. A=1 & B=1

D. AÅB =1                                   4. A=1 & B=0

Codes :

      A         B         C         D

a)   1          2          4          3

b)   2          3          4          1

c)   1          3          2          4

d)   2          4          1          3


63) In the following question, match each of the items A,B and C on the left with an approximation item on the right.

A. Shift Register can be used       1. for code conversion.

B. A multiplexer can be used        2. to generate memory slip to select

C. A decoder can be used             3. for parallel to serial conversion

                                                      4. as many to one-switch

                                                      5. for analog to digital conversion.

Codes :

      A         B         C        

a)   1          2          3         

b)   3          4          1

c)   5          4          2         

d)   1          3          5         


64) 64) Match List – I with List – II and select the correct answer using the codes given below the lists:

List – I                                                List - II

            A. 45                                       1. 10110100

            B. 90                                       2. 11010010

            C. 180                                     3. 01011010

            D. 210                                     4. 00101101

                                                            5. 10101000

Codes :

      A         B         C         D

a)   3          4          5          2

b)   4          3          1          2

c)   4          3          5          2

d)   3          4          2          1

65) Which is the most appropriate match for the items in the first column with the items in the second column.

X. Indirect Addressing                 I. Array Implementation

Y. Indexed Addressing                II. Writing relocatable code

Z. Base Register Addressing        III. Passing array as parameter.

a)      (X,III) (Y,I) (Z,II)

b)      (X,II) (Y,III) (Z,I)

c)      (X,III) (Y,II) (Z,I)

d)     (X,I) (Y,III) (Z,II)


66) True/False

1. A finite state machine with 255 states can be implemented by using 13 flip-flops.

2. Ripple counter is another name for a asynchronous counter.

3. Ab+cb+ac can be reduced to ab+cb   

4. A decoder is used for horizontal microinstruction.                                                       

a)      TTTT

b)      FFFF

c)       TFTF

d)      TTTF

67) True/False

1. Flip-flops consist of two cross connected NAND or NOR gates               

2. Computers cannot be considered as programmable calculators.           

3. The Roman number system is a place value number system.

4. Number systems using digits 0 to 5 have a base 5

a)      TTTT

b)      FTTF

c)      TFFF

d)     TTTF

68) True/False

1. A megabyte is about million bytes.

2. BCD code uses only 0s, 1s and 2s.        

3. The basic computing unit in a micro computer is a transistor flip flop.

4. Program counter counts the number of instructions in a computer.    

a)      TTTT

b)      FFFF

c)       TFTF

d)      TFFF

69 True/False

1. In a k- map of four variables A, B, C and D, the term AB will cover a strip of 2 squares.

2. R-2R Ladder DAC is an alternative to the binary-weighted-input DAC.

3. The complement of a product form of an expression is not equal to the sum of the complements.     

4. An inverter changes a LOW level to a HIGH level and vice versa                                            

a)      TTTT

b)      FTFT

c)       TFTF

d)      TTTF

70) True/False

1. Synchronous data transfer is less expensive than asynchronous data transfer.

2. The CPU program counter keeps track of the time of the next program instruction to be executed.

3. During the decoding stage the decoder in the program memory interprets the opcode that currently resides in the instruction register.

4. A program composed of symbolic statements in sometimes called a source program.

a)      TTTT

b)      FFTF

c)       TFTF

d)      TTTF

71) True/False

1. There are flip-flops with asynchronous inputs.

2. The serial in parallel out shift register can be used as serial in serial out register.

3. Registers are addressable by programs            

4. The flip-flop has two outputs, which are always the complement of each other            

a)      TTTT

b)      FFFF

c)       TFTF

d)      TTTF

72) True/False

1. Counters and time delays can be designed using software.    

2. The Gray code is an unweighted code.

3. The flip-flop is a storage device.

In ASCII, decimal digits are represented by 8421 BCD code preceded by 011.

a)      TTTT

b)      FFFF

c)       TFTF

d)      TTTF

73) A full adder is a logic circuit which can add two single order bits plus a carry in from a previous adder. Its incomplete truth table is given in the table below. The missing entry in the outputs for SUM and CARRY out are

















































a)      0 0

b)      0 1

c)      1 0

d)     1 1

74) A computer uses 8 digit mantissa and 2 digit exponent. If a = 0.052 and b=28E + 11 , then b+a-b will

a)      result in an overflow error

b)      result in an underflow error

c)      be 0

d)     be 5.28E + 11

75) The quantity 837 in excess – 3 BCD code would be represented by

            a) 1001            0011    0111

            b) 1000            0001    1001

            c) 1011            0110    1010

            d) 1000            0011    0111