7. Special instructions in instruction sets

7.1 Support for decimal calculation

Business applications involve exact operations on decimal data, which can only be achieved with decimal operations. Instruction sets can provide support for such "rounding-free" decimal operations.

IA-32 still contains DAA and DAS instructions dating from 8086, which, after binary addition (or subtraction) instructions of two 8-bit registers each containing two decimal digits (in binary-coded decimal), adjust the result of the binary addition to give the correct result. The underlying...