23 Jun
2016
23 Jun
'16
9:09 a.m.
On Jun 23, 2016, at 11:17 AM, Chuck Guzis <cclist
at sydex.com> wrote:
...
Of course, there were also machines that used the floating point
facility for all arithmetic. Integer computations is performed as a
subset of floating-point. This has the ramification that an integer
does not occupy an entire word, but only part of it.
The CDC 6000 did that in part. It has full 60 bit integer add/subtract, but multiply and
divide are done using the floating point operations so they work only for numbers up to 47
bits.
The Electrologica X8 is yet another take on this. There, the mantissa is viewed as an
integer, and the normalization rule is to make the exponent as close to zero as possible
without losing bits. The consequence is that all integral values under 2**40 are
represented as exponent zero and the mantissa equal to the number, which amounts to simply
the integer representation of that number. This makes conversion from float to integer
rather easy (and of course, conversion in the other direction takes no code at all).
paul