BCD to decimal — decode the packed BCD value. Task: Convert the BCD bitstream 0101 0110 1001 (bcd) into its decimal number.

Introduction / Context:
Binary Coded Decimal (BCD) represents each decimal digit independently using a 4-bit nibble. Decoding BCD is common in digital clocks, calculators, and interfaces where human-readable decimal is required without complex conversions.

Given Data / Assumptions:

• BCD stream: 0101 0110 1001
• Each nibble encodes one decimal digit 0–9
• No invalid BCD digits appear (1010–1111 would be invalid)

Concept / Approach:
Split the bitstream into 4-bit groups and translate each nibble to its decimal digit using 8-4-2-1 weights. Concatenate the resulting digits to form the final decimal number (not binary interpretation).

Step-by-Step Solution:

Verification / Alternative check:
Cross-check weights: 0101 = 4+1=5; 0110 = 4+2=6; 1001 = 8+1=9. None of the nibbles exceed 1001, so all are valid BCD digits. Therefore, the decoded decimal is 569.

Why Other Options Are Wrong:

• 539 / 596: one or more nibbles misread.
• 2551 / 1552: treat the stream as binary groups wrongly or mix decimal positions.

Common Pitfalls:

• Attempting to interpret the entire 12-bit word as a binary integer; BCD is digit-wise, not value-packed like pure binary.

Final Answer:
569