Assembler : why BCD exists?

assembly x86 cpu-architecture dataformat bcd
llazzaro picture llazzaro · Mar 1, 2010 · Viewed 7.7k times · Source

I know BCD is like more intuitive datatype if you don't know binary. But I don't know why to use this encoding, its like don't makes a lot of sense since its waste representation in 4bits (when representation is bigger than 9).

Also I think x86 only supports adds and subs directly (you can convert them via FPU).

Its possible that this comes from old machines, or other architectures?

Answer

Paul R picture Paul R · Mar 1, 2010

BCD arithmetic is useful for exact decimal calculations, which is often a requirement for financial applications, accountancy, etc. It also makes things like multiplying/dividing by powers of 10 easier. These days there are better alternatives.

There's a good Wikipedia article which discusses the pro and cons.

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