I/BCA/104 Student's Copy
Professional Course Examination, November 2018
1st Semester
BACHELOR OF COMPUTER APPLICATIONS
Course BCA-104
Digital Computer Fundamentals
Revised
Full Marks 75
Time 3 hours
PART A—OBJECTIVE
Marks 25
The figures in the margin indicate full marks for the questions
SECTION—A
Marks 15
Tick the correct answer in the brackets provided 1×10=10
1. The complement of (636)10 is
336
363
663
373
/362 1 Contd.
2. When an input electrical signal A 10100 is applied to a NOT gate, its
output signal is
01011
10001
10101
00101
3. Conversion of binary number 1011012 to hexadecimal is
3716
2E16
2716
2D16
4. Flip-flop outputs are always
the same
independent of each other
complimentary
same as inputs
5. A half-adder adds bits.
16
8
4
2
I/BCA/104 2 Contd.
6. A demultiplexer is also known as
data selector
data distributor
decoder
encoder
7. A shift register can be used for
parallel to serial conversion
serial to parallel conversion
digital delay line
All of the above
8. Binary Coded Decimal numbers express each digit as a
byte
bit
nibble
None of the above
9. Multiplication of 1112 by 1012 is
1100112
1000112
1111002
0001012
I/BCA/104 3 Contd.
10. A combinational logic circuit that selects one of several digit inputs and
forwards the selected input into a single line is
multiplexer
decoder
encoder
demultiplexer
Indicate whether the following statements are True or False by putting
a Tick mark in the brackets provided 1×5=5
1. A decoder is used to change a BCD number into an equivalent decimal
number.
T F
2. The hexadecimal number system is widely used in analyzing and
programming microprocessor.
T F
3. The D flip-flop is a modification of R-S flip-flop.
T F
4. A BCD counter is a decade counter.
T F
5. An OR gate output is low only if all the inputs are high.
T F
I/BCA/104 4 Contd.
SECTION—B
Marks 10
Answer the following questions 2×5=10
1. Differentiate between register and counter.
2. Simplify D ¢ D
3. Explain overflow.
4. From the given expression, draw the logic symbol and truth table
Exp A B ¢ ×C ¢ D
5. What is encoder?
PART B—DESCRIPTIVE
Marks 50
The figures in the margin indicate full marks for the questions
1. Convert the following 6
(17)10
(101011)2 )10
(7013)8 )10
Explain the compliment and compliment. What is the 10's
compliment of (0·3267)10? 4
OR
Write the block diagram of a digital computer and explain its units. 6
Convert (100101100101101011)2 to octal and hexadecimal numbers. 4
I/BCA/104 5 Contd.
2. Explain any five digital logic gates with names, graphic symbols and
truth table. 5
Simplify the following expression, using four variable K-map in sum of
product form 5
f D S
OR
Draw the logic circuit for Y ABC ABC ¢. Simplify the equation with
Boolean algebra and draw the simplified logic circuit. 6
Express the Boolean function F x yz in a sum of minterm form. 4
3. What is multiplexer? Write the logic and draw the block diagram of a
4-to-1 line multiplexer. 6
Explain half-adder by showing its truth table and implementation
using logic gates. 4
OR
What is decoder? Design a 3-to-8 line decoder showing its truth table. 6
Explain demultiplexer with suitable diagram. 4
4. Explain the working of J-K flip-flop giving its logic diagram and its
characteristics table. 6
Explain shift register with block diagram. 4
OR
Explain the working of R-S flip-flop giving its logic diagram and its
characteristics table. 6
Differentiate between asynchronous counter and synchronous
counter. 4
I/BCA/104 6 Contd.
5. Explain the following 6
Arithmetic micro operation
Logic micro operation
Shift micro operation
Differentiate between bus transfer and memory transfer. 4
OR
Explain macro operation and micro operation with diagram. 6
Differentiate between fixed point binary data and floating point data. 4