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BCD code advantages and disadvantages

Short answer

BCD codes each decimal digit 0–9 as 4‑bit 8421 binary. Advantages: easy decimal conversion, exact representation of decimal fractions, simple display interfacing. Disadvantages: uses more bits, six invalid codes, arithmetic needs correction (add 6) making circuits slower and more complex.

What is BCD code? List the advantages and disadvantages of BCD code.

BCD (Binary Coded Decimal) is a code in which each decimal digit 0–9 is represented by its own 4-bit binary value with weights 8-4-2-1. Codes 1010–1111 are invalid. Example: (57)10(57)_{10} = 0101 0111 (BCD).

Advantages

  1. Very easy conversion between decimal and BCD, as each digit is coded separately.
  2. Suitable for decimal displays (7-segment), calculators, digital clocks and meters, where numbers are shown to people.
  3. Decimal fractions such as 0.1 are represented exactly, so it is used in financial calculations.
  4. Easy to scale by powers of 10 (shift by one digit).

Disadvantages

  1. Needs more bits than pure binary: (99)10(99)_{10} needs 8 bits in BCD but only 7 in binary; storage is wasted.
  2. Six of the 16 4-bit combinations are unused.
  3. Arithmetic is more complex: after binary addition a correction (add 0110) is needed when a digit exceeds 9.
  4. Circuits for BCD arithmetic are slower and more complex than binary circuits.

✓ Answer checked by Claude Opus 5.5 (high effort)

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