Status of the process
D ---> Uninterruptible sleep (usually IO) R ---> Running or runnable (on run queue) S ---> Interruptible sleep (waiting for an event to complete) T ---> Stopped, either by a job control signal or because it is being traced. W ---> paging (not valid since the 2.6.xx kernel) X ---> dead (should never be seen) Z ---> Defunct ("zombie") process, terminated but not reaped by its parent.
and the additional characters are:
< ---> high-priority (not nice to other users) N ---> low-priority (nice to other users) L ---> has pages locked into memory (for real-time and custom IO) s ---> is a session leader l ---> is multi-threaded (using CLONE_THREAD, like NPTL pthreads do) + ---> is in the foreground process group