What is advantages and disadvantage of bcd?

Answer 1

Advantage of bcd are:

• One advantage of BCD over binary representations is that there is no limit to the size of a number. To add another digit, just add a new 4-bit sequence.
• Numbers represented in pure binary format are limited to the largest number that can be represented by 8, 16, 32 or 64 bits.
• Sometimes, the right-most nibble contains the sign (positive or negative).
• It is easier to convert decimal numbers to and from BCDthan binary and, though BCD is often converted to binary for arithmetic processing, it is possible tobuild hardware that operates directly on BCD.
• Disadvantage of bcd are:
• • Some operations are more complex to implement. Adders require extra logic to cause them to wrap and generate a carry early. 15-20 percent more circuitry is needed for BCD add compared to pure binary. Multiplication requires the use of algorithms that are somewhat more complex than shift-mask-add (a binary multiplication, requiring binary shifts and adds or the equivalent, per-digit or group of digits is required)
  • Standard BCD requires four bits per digit, roughly 20 percent more space than a binary encoding (the ratio of 4 bits to log210 bits is 1.204). When packed so that three digits are encoded in ten bits, the storage overhead is greatly reduced, at the expense of an encoding that is unaligned with the 8-bit byte boundaries common on existing hardware, resulting in slower implementations on these systems.
  • Practical existing implementations of BCD are typically slower than operations on binary representations, especially on embedded systems,due to limited processor support for native BCD operations.