ISRO | ISRO CS 2014 | Question 27

How many different BCD numbers can be stored in 12 switches? (Assume two position or on-off switches)
(A) 2¹²
(B) 2¹²-1
(C) 10¹²
(D) 10³

Answer: (D)
Explanation: In Binary Coded Decimal (BCD) encoding scheme each of the decimal numbers(0-9) is represented by its equivalent binary pattern (which is generally of 4-bits).

A switch can store 1 bit, either 0 (off) or 1 (on) and each digit of BCD representation takes 4 bits, so there will be 12/4 = 3 BCD digits. A BCD digit can be from 0 to 9 (total 10 possibility).

Therefore, different possible BCD numbers in 12 switches are:
= 10 * 10 * 10 = 1000 = 10³

So, option (D) is correct.

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