Number Systems and Codes Interview Questions and Answers:

1. What is meant by radix (or base) of a number system?

Ans. Radix or base of a number system is the number of digits or distinct symbols it uses to represent various numbers.

2. What is meant by LSB and MSB?

Ans. The right most bit of a binary number is called least-significant bit (LSB) while the left most bit of a binary number is known as most-significant bit (MSB).

3. Define octal and hexadecimal number systems.

Ans. The number systems with base (or radix) 8 and 16 are known as octal number system and hexadecimal number system respectively.

4. What is octal number?

Ans. The number with base (or radix) eight is known as octal number

5. Why hexadecimal code is widely used in digital systems?

Ans. It is very convenient to enter binary data in a digital system using hex code.

6. What is meant by BCD code?

Ans. BCD code is a decimal system with each digit encoded in its binary equivalent of 4 bits.

7. What is an excess-3 code?

Ans. Excess-3 code is derived from the natural BCD code by adding 3 (0011) to each coded number.

8. Why hexadecimal code is widely used in digital systems?

Ans. It is very convenient to enter binary data in a digital system using hex code.

9. What is the difference between binary code and BCD?

Ans. BCD is not a number system like binary. It is a decimal system with each decimal digit encoded in its binary equivalent. A straight binary code takes the complete decimal number and represents it in binary while the BCD code converts each decimal digit to binary individually.

10. State the disadvantage of a 8-4-2-1 code.

Ans. BCD requires more bits than straight binary to represent decimal numbers of more than one digit. This is because BCD does not use all possible 4-bit groups and is, therefore, inefficient.

11. Why is an excess-3 code called an unweighted code ? What will be excess-3 code for decimal 5849.

Ans. Since no definite weights can be assigned to the four digit positions in an excess-3 code, it is an unweighted code.

(5849)10 = (1000 1011 0111 1100)XS-3

12. Explain the use of excess-3 code.

Ans. The key feature of the excess-3 code is that it is self-complementing code. It means that 1’s complement of the coded number yields 9’s complement of the number itself. The self-complementing property makes the excess-3 code useful in some arithmetic operations, because subtraction can be performed using 9′ complement method and 1’s complement can be easily produced with digital logic circuits by simply inverting each bit.

13. What are the advantages of Gray code?

Ans. In Gray code, if we go from any one decimal number to the next, only one bit of the Gray code changes. Because of this feature, an amount of switching is minimized and the reliability of the switching systems is improved.

14. What is an alphanumeric code?

Ans. The codes used for representing letters of alphabet, punctuation marks and other special characters along with numbers are called alphanumeric codes.

15. Which is the most commonly used code for representing alphanumeric information?

Ans. ASCII (American Standard Code for information Interchange) is the most widely used alphanumeric code. It is a 7-bit code.

16. Explain what do you understand by parity bit? What are the two types of parity bit?

Ans. The simplest technique for detecting a single error is that of add­ing an extra bit, known as parity bit, to each word being transmit­ted. It can follow either odd parity code or even parity code.