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<footer class="replyforwardcontainer"><span>On Fri, 15 Jan 2021 14:37:35 -0800, peter@easthope.ca wrote:</span><br>
<br>
> From: Charles Perkins <chuck@kuracali.com><br>
> Date: Fri, 15 Jan 2021 13:17:03 -0800<br>
>> On review of the source, I see that LONGREAL is currently aliased to REAL<br>
>> in ORB, suggesting that REAL may stay 32-bit and LONGREAL would be 64-bit.<br>
>> Would the same be done for SET, introducing LONGSET perhaps?<br>
><br>
> From the new Project Oberon book I had the impression that the gain of<br>
> one type rather than two outweighed the loss of storing some numbers<br>
> in capacities larger than necessary.<br>
><br>
> If so, wouldn't any machine have only REAL, according to hardware<br>
> capability, whether 32 bits or 64 bits or 128 bits?<br>
><br>
> What are the requirements motivating interest in 64 bits? Numerical<br>
> modeling?</chuck@kuracali.com><br>
<br>
32-bit REAL means 24 bits of mantissa and 8 bits of exponent. This just isn't enough to give acceptable numerical stability or precision. On simple 32-bit machines, the answer is double precision, or LONGREAL, which gives 48 bits of mantissa and 16 bits of exponent, which is acceptable.<br>
<br>
By contrast, the Control Data 6600 (and its little brother, the 6400, where PASCAL started) had a 60-bit word. 60-bit REAL on the 6600 gave 12 bits of exponent and 48 bits of mantissa, which was good enough right out of the box. I don't recall the details of 6600 double precision.</footer>
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