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
- Decimal-Binary Conversion
- BCD Multifunctional Modular Counter