# Education In Pakistan

## VU CS302-Digital Logic Design (S1) MIDTERM EXAMINATION SEMESTER SPRING 2005

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MIDTERM EXAMINATION SEMESTER SPRING 2005

CS302-Digital Logic Design (S1)

Total Marks:50

Duration:60 Min

Name

PVC Name / Code

Date

Maximum Time Allowed: (1 Hour)

questions:

1. Attempt all questions.

2. Calculators are NOT allowed.

3. Do not ask any questions about the contents of this examination from anyone.

a. If you think that there is something wrong with any of the questions,

attempt it to the best of your understanding.

b. If you believe that some essential piece of information is missing, make an

appropriate assumption and use it to solve the problem.

4. Circuit Diagrams, Equations and Truth Tables should be clear.

Write down all the steps in Subjective Questions. Marks will be deducted for

missing steps.

**WARNING: Please note that Virtual University takes serious note of unfair means.

Anyone found involved in cheating will get an `F` grade in this course.

.

For Teacher’s use Only

Question Q1 Q2 Q3 Q4 Q5 Total

Marks

Question No: 1 Marks: : 2+2+2+2+2=10

Select the best possible choice.

a) A NOR’s gate output is HIGH if

I. all inputs are HIGH

II. any input is HIGH

III. any input is LOW

IV. all inputs are LOW

b) A demultiplexer has

I. one input and several outputs

II. one input and one output

III. several inputs and several outputs

IV. several inputs and one output

c) The difference of 111 – 001 equals

I. 100

II. 111

III. 001

IV. 110

d) To implement the expression ABCD ABCD ABCD , it takes one OR gate and

I. three AND gates and three inverters

II. three AND gates and four inverters

III. three AND gates

IV. one AND gate

e) Which gate is best used as a basic comparator?

I. NOR

II. OR

III. exclusive-OR

IV. AND

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Question No: 2 Marks: 10

Convert (-7A) 16 into Binary number system and then take 2’s complement of the resultant binary

number. (Show all necessary steps.)

Question No: 3 Marks: 10

Implement a logic circuit for the truth table given below:

INPUTS OUTPUTS

A B C X

0 0 0 1

0 0 1 0

0 1 0 1

0 1 1 0

1 0 0 1

1 0 1 0

1 1 0 1

1 1 1 1

Question No: 4 Marks:6+4=10

a) Draw a 4-variable K-map and label each cell according to its binary value.

(Hint) for 2 –variable k-map

A\B 0 1

0 00 01

1 10 11

b) Expand each expression to standard SOP form.

ABCD ACD BCD ABCD

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Question No: 5 Marks: 4+6=10

Draw a truth table and circuit diagram of 4 bit parallel adder?

## VU CS302-Digital Logic Design (S1) MIDTERM EXAMINATION SEMESTER SPRING 2005

.

MIDTERM EXAMINATION

SEMESTER SPRING 2005

CS302-Digital Logic Design (S1)

Total Marks:50

Duration:60 Min

Maximum Time Allowed: (1 Hour)

questions:

1. Attempt all questions.

2. Calculators are NOT allowed.

3. Do not ask any questions about the contents of this examination from anyone.

a. If you think that there is something wrong with any of the questions,

attempt it to the best of your understanding.

b. If you believe that some essential piece of information is missing, make an

appropriate assumption and use it to solve the problem.

4. Circuit Diagrams, Equations and Truth Tables should be clear.

Write down all the steps in Subjective Questions. Marks will be deducted for

missing steps.

**WARNING: Please note that Virtual University takes serious note of unfair means.

Anyone found involved in cheating will get an `F` grade in this course.

.

For Teacher’s use Only

Question Q1 Q2 Q3 Q4 Q5 Total

Marks

Question No: 1

Select the best possible choice.

a) A NOR’s gate output is HIGH if

Marks: : 2+2+2+2+2=10

I.

II.

III.

IV.

all inputs are HIGH

any input is HIGH

any input is LOW

all inputs are LOW

b) A demultiplexer has

I.

II.

III.

IV.

one input and several outputs

one input and one output

several inputs and several outputs

several inputs and one output

c) The difference of 111 – 001 equals

I. 100

II. 111

III. 001

IV. 110

d) To implement the expression ABCD ABCD ABC D , it takes one OR gate and

I. three AND gates and three inverters

II. three AND gates and four inverters

III. three AND gates

IV. one AND gate

e) Which gate is best used as a basic comparator?

I.

II.

III.

IV.

NOR

OR

exclusive-OR

AND

.

Question No: 2 Marks: 10

Convert (-7A) 16 into Binary number system and then take 2’s complement of the resultant binary

number. (Show all necessary steps.)

Question No: 3 Marks: 10

Implement a logic circuit for the truth table given below:

INPUTS OUTPUTS

A B C X

0 0 0 1

0 0 1 0

0 1 0 1

0 1 1 0

1 0 0 1

1 0 1 0

1 1 0 1

1 1 1 1

Question No: 4 Marks:6+4=10

a) Draw a 4-variable K-map and label each cell according to its binary value.

(Hint) for 2 –variable k-map

b) Expand each expression to standard SOP form.

ABCD AC D BCD ABC D

A\B 0 1

0 00 01

1 10 11

.

Question No: 5 Marks: 4+6=10

Draw a truth table and circuit diagram of 4 bit parallel adder?