How do you find the amount of RAM free?

[Andrew Phillips]

We will shortly have many more users here and I need to determine how
much RAM various programs use.  It would also be nice if we could
tell at any time how much RAM is unused.  Using malloc() is
useless since the most I can malloc() is always about 4.7 Mbytes,
because of virtual memory.

On a similar vein.  Is it possible to tell the system to use some
memory areas before others.  We can have a maximum of 8 Mbytes of 32
bit memory.  If we go beyond and add 16 bit memory then we would want
it used after the 32 bit RAM.

Any help would be most appreciated.
-- 
Andrew Phillips (andrew at teslab.lab.oz.au) Phone +61 (Aust) 2 (Sydney) 289 8712