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0 pointsblattimwind6y ago0 comments

> There's also BCD (binary coded decimal) that can solve some problems by avoiding the decimal-to-binary conversions if you're mainly dealing with decimal values. For instance 0.2 can't usually be represented in binary but of course it poses no problem in BCD.

BCD is/was super common in measurement equipment for internal calculations for this reason, and also because it is trivial to format for display (LED/LCD/VFDs) or text output (bus system, printer/plotter).

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dspillett6y ago

Many CPUs support BCD, at least in a limited number of ways compared to their normal binary representation.

The 8086 (and its descendants, of course) supports BCD by having instructions to adjust the result after the basic add/sub/mul/div instructions, though only one byte at a time.

The 6502's add and subtract instructions would operate on, and output, BCD values if the special purpose "decimal" flag was set. Again only in 8-bit (two digit) chunks but that is to be expected as it was an 8-bit chip generally.

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0 pointsblattimwind6y ago0 comments

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dspillett6y ago

Many CPUs support BCD, at least in a limited number of ways compared to their normal binary representation.

The 8086 (and its descendants, of course) supports BCD by having instructions to adjust the result after the basic add/sub/mul/div instructions, though only one byte at a time.

j / k navigate · click thread line to collapse