BCD stands for Binary Coded Decimal. It is a form of representing decimal numbers using a binary code. In BCD, each decimal digit is represented by a 4-bit binary code. Let's break down the answer and explain why it is option 'B' - 4 bits.

Binary Coded Decimal (BCD)

BCD is a way of representing decimal digits using a binary code. In BCD, each decimal digit is represented by a 4-bit binary code. This means that 4 binary bits are required to represent a single BCD digit.

Binary Digits

In binary representation, each digit can take on one of two values, 0 or 1.

Decimal Digits

In decimal representation, each digit can take on one of ten values, from 0 to 9.

BCD Representation

To represent decimal digits using BCD, each decimal digit is divided into its binary equivalent. For example, the decimal digit 0 is represented as 0000 in BCD, 1 as 0001, 2 as 0010, and so on up to 9 as 1001.

Number of Bits for a BCD Digit

Since each decimal digit is represented by a 4-bit binary code in BCD, we can conclude that 4 bits are required to store one BCD digit.

Examples

Let's consider some examples to further illustrate this:

- The BCD representation of the decimal digit 3 is 0011, which requires 4 bits.
- The BCD representation of the decimal digit 7 is 0111, which also requires 4 bits.
- The BCD representation of the decimal digit 9 is 1001, again requiring 4 bits.

Conclusion

In conclusion, 4 bits are required to store one BCD digit. This is because each decimal digit is represented by a 4-bit binary code in BCD. Therefore, the correct answer is option 'B' - 4 bits.