MEM

Display memory usage.

Syntax
      MEM 
      MEM /C
      MEM /D
      MEM /P

Key
   /P   List programs in memory
        with the memory address and size of each 

   /D   List Programs(as /P) and also Devices

   /C   List programs in conventional memory and
        list programs in upper memory

MEM will only display details about the current CMD shell environment, programs running in a separate shell (or WIN32 programs) will not be listed - so it won't tell you anything about total memory usage.

"The palest ink is better than the sharpest memory" - Chinese proverb

Related Commands:

CLEARMEM (Resource Kit) - Clear Memory Leaks
WINMSD - Windows NT Diagnostics (including Physical Memory)
GUI Task Manager - for all program details including Win32 applications.
TLIST - Task List
Q184419 - DisablePagingExecutive (use when >500M RAM is available)
Q126962 - How to increase desktop heap memory for non-interactive processes
/3GB Startup Switch for Windows 2003

Equivalent Linux BASH commands:

free -t - Display a summary of current memory usage and availability.