Microcode, which is a no-go for modern designs

[Fred Cisin]

>> Few people (but most are right here) can recite PI to enough digits to
>> reach the level of inaccuracy.   And those who believe that PI is exactly
>> 22/7 are unaffected by FDIV.   (YES, some schools do still teach that!)

On Mon, 7 Jan 2019, Johnny Eriksson via cctalk wrote:
> Why remember the digits, when a small program can provide them?
>
>  +0un qn"E20Un' 0Uh 0uv HK
>  Qn<j 0uq Qn*10/3Ui
>  Qi<\+2*10+(Qq*qi)Ua 0LK Qi*2-1Uj Qa/QjUq Qa-(Qq*Qj)-2\10I$ Qi-1ui>
>  Qq/10Ut Qh+Qt+48Uw Qw-58"E48Uw %v' Qv"N:Qv,1^T' QwUv Qq-(Qt*10)Uh>
>  :Qv,1^T
>  !Can you figure out what this macro does before running it?  It was
>  written by Stan Rabinowitz with modifications by Mark Bramhall and
>  appeared as the Macro of the Month in the Nov. 1977 issue of the TECO
>  SIG newsletter, the "Moby Munger".  For information on the TECO Special
>  Interest Group, write to Stan at P.O. Box 76, Maynard, Mass. 01754!

Interesting bit!


> Why remember the digits, when a small program can provide them?

Maybe, because remembering the first 80 or 90 digits is half as much work 
to remember or type in, as that macro.


The current state of computer "science" "education" fails to even get the 
students to understand that floating point is a rounded off approximation. 
FDIV merely added a small unexpected further degradation to a 
representation that was already inaccurate, and was explicitly an 
approximation.
They often represent a dollar and cents amount as floating point, just to 
avoid figuring out how to insert the PERIOD delimiter.  Use of FDIV is 
inappropriate for calculating sales tax.  NOT because of the FDIV errors, 
which are well within the portion that will be discarded in roundoff.
It should not take until a third semester "Data Structures And Algorithms" 
class, or beyond, for them to learn to not use floating point for cash 
transaction processing.

People who use 3.1416 or 22/7 for PI are not in a position to gripe 
as much as they did, about inaccuracies caused by FDIV.
The point was that people were screaming about errors that were already 
irrelevant to the level of accuracy that they were using, in uses that 
were explicitly NOT INTENDED to be exact.


I am building a base to make a patio table out of a CRASHED 24" RAMAC 
platter, that had been banged around with no effort to store properly for 
half a century.  (Is there a better use for a CRASHED platter?, or a 
better way to display it than under glass as a rustic table top?) 
Neither a value of 3.14 for PI, nor FDIV, will further degrade my level of 
carpentry skills.
I'm considering printing out and including a copy of the RAMAC plaque
http://www.ed-thelen.org/RAMAC/RAMAC_Plaque_v40.pdf