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Comp 008: Introduction Of Digital Logic And Data Communications Question Paper

Comp 008: Introduction Of Digital Logic And Data Communications

Course:Certificate In Computer Science

Institution: Chuka University question papers

Exam Year:2013

CHUKA

UNIVERSITY

UNIVERSITY EXAMINATIONS
EXAMINATIONS FOR THE AWARD OF CERTIFICATE IN COMPUTER SCIENCE
COMP 008: INTRODUCTION OF DIGITAL LOGIC AND DATA COMMUNICATIONS
STREAMS: CERT. (COMP.SCI) YIS2 TIME: 2 HOURS
DAY/DATE: WEDNESDAY 24/4/2013 11.30 AM – 1.30 PM
INSTRUCTIONS:

ANSWER QUESTION ONE AND ANY OTHER TWO QUESTIONS

QUESTION ONE COMPULSORY (30 MARKS)

(a) Define the following terms giving examples where applicable. [12 Marks]

(i) Logic gates
(ii) Register
(iii) Truth table
(iv) Decoder.

(b) Give the standard logic symbols and a description of the operation of each of the following gates.

(i) AND gage
(ii) NOT gate
(iii) OR gate. [9 Marks]

(c) Multiply to obtain a sum of products.

(A+B^'' C+D^'' )(B^'' C+D^''+E)(A+E^'' )(AD+E'' [5 Marks]

1
(d) Which of these combinational logic devices are considered to be “universal” gates?
[2 Marks]
Multiplexers
NANDs
XORs
NORs

(e) Which of these Boolean equations are correct? [2 Marks]
(a) A+1=A
(b) A?¦1=A ¯
(c) A.1=A
(d) (AB) ¯=A ¯+B ¯

SECTION TWO (ANSWER ANY TWO QUESTIONS)

Question Two (20 Marks)

(a) Simplify the following expressions.

XZ+YV(X^''+Z)+XZ^'' [4 Marks]

A^'' B^'' C+(A^'' B^'' C)'' [3 Marks]

(b) From the following truth table below determine the standard SOP expression. [5 Marks]

INPUT OUTPUT
ABC X
000 0
001 1
010 0
011 1
100 0
101 0
110 1
111 0

(c) Realize the function and draw the network using two OR gates and two AND gates.
(8 Marks)
f=(v+w+x)(v+x+y)(v=z)

QUESTION THREE (20 MARKS)

(a) Explain the following concepts in data communication, and give appropriate examples or
diagrams in each case? [6 Marks]

Frequency modulation
Amplitude modulation
Phase modulation

(b) Explain the following concepts in data communication, and give appropriate examples in each case. [9 Marks]

(i) Simplex
(ii) Half-Duplex
(iii) Full-duplex

(c) Using theorems of Boolean algebra, prove the following: [5 Marks]
BD^'' E+ABCE+CDE=BD^'' E+CDE

QUESTION FOUR (20 MARKS)

(a) A Boolean function is given by:
F=AB+(BC) ¯
Draw a implementation of the circuit using logic gates. [8 Marks]

(b) Draw a truth table for each of the following: [12 Marks]

(i) A+B=F
(ii) A=B
(iii) AB=F
A NOR B=F

QUESTION FIVE (20 MARKS)

“Errors” can arise in a communication circuit from a variety of causes. Such errors may lead to degradation of the transmitted signal. Thus the receiving end cannot correctly determine what was sent.
(a) List many conditions that can cause errors on a communication line. [4 Marks]

(b) Describe the various error detection methods that can be put in place. [8 Marks]

(c) Describe what can be done to correct errors to maintain data integrity. [8 Marks]

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Comp 008: Introduction Of Digital Logic And Data Communications Question Paper

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