[TUHS] arithmetic IF (was origin of string.h and ctype.h)

[Doug McIlroy]

> According to the Wikipedia article on FORTRAN, CAS was usually not the
> most efficient way to implement arithmetic IF anyway.  CAS takes up
> four words of memory and takes three cycles to execute, whereas you
> can do it in two words and two cycles with the transfer instructions.

Though the article's conclusion was right, its numbers were wrong. 
As a correct discussion of possible implementations of arithmetic-IF
would be long and essentially off topic, I have chopped most of it
out of the article.

doug