On Wed, Oct 26, 2011 at 13:48, Vintage
Coder<vintagecoder at aol.com>  wrote:
  I was thinking about this recently and I
can't come up with a definition either. Maybe anything smaller than the smallest
mainframe and bigger than the biggest PC?
  People who know about this stuff just
"know". 
 Agreed. 
 I recall there was a semi-serious list at some point (possibly here,
 maybe on a.f.c.):
 If you can lose a screwdriver in it, it might be a micro.
 If you can lose a voltmeter in it, it might be a mini.
 If you can lose a 'scope on a cart in it, it might be a mainframe.
 There was more to it.  Fuzzy memory.
 
Back around 1980, the criteria DoD used:
        under USD 100K - micro
        under USD 1M   - mini
        over  USD 1M   - mainframe
this was based on purchase price, since many systems were leased.
Just about every industry had its own criteria - usually an arbitrary
definition by either the bean counters or <mis>management.