Practical Electronics/Binary-coded Decimal

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Binary-coded Decimal or BCD is a way of representing a decimal number as a string of bits suitable for use in electronic systems. Rather than converting the whole number into binary, BCD splits the number up into its digits and converts each digit to 4-bit binary.

Thus, for example, 345 becomes

0011 0100 0101

This is 3 digits longer than the real binary equivalent of 345, 101011001, but it has several advantages:

  • It can easily be used to drive displays, as each digit is encoded separately.
  • It allows each conversion to decimal; true binary to decimal conversion is difficult and gets increasingly difficult as the number gets longer.
  • It allows easy scaling by factors of 10

It also has disadvatages:

  • It is difficult to perform arithmetic operations (such as adding) on BCD numbers, as it is not as easy to recognise carries, etc.
  • It is longer than true binary, and so require more storage space.


SEveral ICs are available to handle BCD counting:

  • 4028 - BCD-to-decimal decoder
  • 4029 - BCD/true-binary counter
  • 4510 - BCD decade counter
  • 4511 - BCD 7-segment display driver

See Also[edit]

  • Binary
  • Decimal-Binary Conversion
  • BCD Multifunctional Modular Counter