Binary-coded Decimal - Other Computers and BCD

Other Computers and BCD

The Digital Equipment Corporation VAX-11 series included instructions that could perform arithmetic directly on packed BCD data and convert between packed BCD data and other integer representations. The VAX's packed BCD format was compatible with that on IBM System/360 and IBM's later compatible processors. The MicroVAX and later VAX implementations dropped this ability from the CPU but retained code compatibility with earlier machines by implementing the missing instructions in an operating system-supplied software library. This was invoked automatically via exception handling when the no longer implemented instructions were encountered, so that programs using them could execute without modification on the newer machines.

In more recent computers such capabilities are almost always implemented in software rather than the CPU's instruction set, but BCD numeric data is still extremely common in commercial and financial applications.

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