cli to track app utilizing CPU

["a s p a s i a" <aspasia pair com>]

hello,

i have 12gig of RAM; checking top i noticed
that i only have aroun 500mb fee memory ...
though it shows percentage of memory utilized
by an app ... is there a CLI that I can use to
exactly trace which application or process is
using most of my memory, and exactly how much?

- a.