Question

question 13
which of the following is an invalid bcd code?
1001
0011
0101
1101

Explanation:

Step1: Recall BCD code rules

BCD (Binary - Coded Decimal) uses 4 - bit binary to represent decimal digits (0 - 9).

Step2: Check each code

• For 1001: \(1\times2^{3}+0\times2^{2}+0\times2^{1}+1\times2^{0}=8 + 1=9\) (valid).
• For 0011: \(0\times2^{3}+0\times2^{2}+1\times2^{1}+1\times2^{0}=2 + 1=3\) (valid).
• For 0101: \(0\times2^{3}+1\times2^{2}+0\times2^{1}+1\times2^{0}=4 + 1=5\) (valid).
• For 1101: \(1\times2^{3}+1\times2^{2}+0\times2^{1}+1\times2^{0}=8+4 + 1=13\). Since BCD only represents 0 - 9 per 4 - bit group, 1101 is invalid.

Answer:

1101