Why use float and double instead of real?

[Don]

Lars T. Kyllingstad wrote:
> Is there ever any reason to use float or double in calculations? I mean, 
> when does one *not* want maximum precision? Will code using float or 
> double run faster than code using real?
> 
> I understand they are needed for I/O and compatibility purposes, so I am 
> by no means suggesting they be removed from the language. I am merely 
> asking out of curiosity.
> 
> -Lars

Size. Since modern CPUs are memory-bandwidth limited, it's always going 
to be MUCH faster to use float[] instead of real[] once the array size 
gets too big to fit in the cache. Maybe around 2000 elements or so.

Rule of thumb: use real for temporary values, use float or double for 
arrays.