Stack and Heap

Are there any commands / functions to call to find out memory info?

For example, if I am writing a program that is using a ton of memory.
Everything is working and then I add more code needing more memory but it
crashes and I think I may be trying to use too much...  Can I call some
commands to see how much memory is left?  And/Or how much I am using?  For
Stack and Heap?


Thank You,

Nate