# Computer Fundamentals Questions and Answers – The Decimal Number System

This set of Computer Fundamentals Interview Questions and Answers for freshers focuses on “The Decimal Number System”.

1. The value of base in a decimal number system is ____________
a) 8
b) 2
c) 10
d) 16

Explanation: A decimal number system consists of 10 digits from 0 to 9.
The definition of base describes it as a quantity to represent the number of digits present in that particular number system.
Therefore, here, the base is 10.

2. Convert : (110)2 = ( __ )10.
a) 4
b) 5
c) 6
d) 9

Explanation: The base 2 represents that the number is binary ,whereas, the base 10 represents that it is to be converted to the decimal format.
Conversion: 22 * 1 + 21 * 1 + 20 *0 = 6.

3. The 2’s complement of 15 is ____________
a) 0000
b) 0001
c) 0010
d) 0100

Explanation: 2’s complement is obtained by adding 1 to the 1’s complement of the number.
Here, Binary of 15 = 1111
1’s complement of 15= 0000
2’s complement of 15= 0000+1=0001.

4. Another name for base is __________
a) root
c) entity
d) median

Explanation: Another name for base is radix. Base refers to the number of digits that a particular number system consists of.
The base of decimal number system is 10, binary is 2 and so on.

5. The decimal equivalent of (0.101)2 will be ____________
a) 0.5
b) 0.625
c) 0.25
d) 0.875

Explanation: Since the base is 2 , it could be easily guessed that the number is binary. Conversion: 2-1 * 1 + 2-2 * 0 + 2-3 * 1 = 0.625.
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6. The signed magnitude for -3 will be ___________
a) 00000011
b) 10000011
c) 11111101
d) 11111100

Explanation: Signed Magnitude of a number is a representation to determine if the number is positive or negative.
If the MSB of a number is 0, the number is positive, else if it is 1 the number is negative.
Here, +3 = 00000011
-3= 100000011.

7. A number with both integer and a fractional part has digits raised to both positive and negative powers of 2 in a decimal number system.
a) True
b) False

Explanation: In a decimal number system, a number with both integer and a fractional part has digits raised to both positive and negative powers of 10 and not 2.
e.g. 22.34 = 2 * 101 + 2 * 100 + 3 * 10-1 + 4 * 10-2.

8. The hexadecimal representation of 14 is _______________
a) A
b) F
c) D
d) E

Explanation: The hexadecimal representations are as follows:
10 : A
11 : B
12 : C
13 : D
14 : E
15 : F.

9. Which of the following is not a decimal number?
a) 114
b) 43.47
c) 99.9A
d) 10101

Explanation: All the numbers except 99.9A are decimal numbers.
This number has a hexadecimal component A in it, therefore , it is not a valid decimal number.
The decimal equivalent of A is 10.

10. Select the incorrect option:
a) (101)10 = (1100101)2
b) G is valid in hexadecimal system.
c) C represents 12
d) The base of a decimal number system is 10.

Explanation: G is not a valid hexadecimal number. In this system, only representations from A to E are used to represent the numbers from 10 to 15. The base of the hexadecimal number system is 16.

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