BCD definition check: Is a decimal number converted to BCD by replacing each decimal digit with a 3-bit binary code?

Introduction / Context:
Binary-Coded Decimal (BCD) is a family of encodings that map each decimal digit 0–9 to its own binary pattern. BCD is widely used in digital displays, financial arithmetic, and interfaces where precise decimal digit handling is required. The question probes whether BCD uses 3-bit groups per digit.

Given Data / Assumptions:

• We refer to standard 8421 BCD unless otherwise specified.
• Digits: 0–9 must be representable individually.
• We are not discussing octal or specialized ternary systems.

Concept / Approach:
Since decimal has 10 symbols (0–9), at least 4 bits are required to encode all digits because 3 bits yield only 8 distinct combinations (0–7). Standard BCD uses 4-bit nibbles, typically 0000–1001 for digits 0–9; the six remaining 4-bit patterns 1010–1111 are invalid in plain BCD (or used for special purposes in some variants).

Step-by-Step Solution:

Verification / Alternative check:
Example: 79 in BCD is 0111 1001 (7 → 0111, 9 → 1001). Any attempt to use 3-bit groups cannot represent digits 8 or 9.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing BCD with binary, octal, or hexadecimal; mishandling invalid BCD codes (A–F) that appear in hex dumps but are not valid decimal digits.

Final Answer:
Incorrect — standard BCD uses a 4-bit code per decimal digit