UNIX - Process State Codes

O - On processor -- the process is executing on the CPU in either user or system mode.
R - Runnable -- the process is on a run queue and is running or runnable. 
S - Sleeping -- the process is waiting for a I/O event to complete. 
Z - zombie -- process, terminated but not reaped by its parent.
T - stopped -- process has been stopped
X - dead -- (should never be seen) 

For more information on process life-cycles click here

Tags: UNIX