What Is a Process? Process States Explained

What a Process Actually Is

A process is a program in execution - not just the code sitting on disk, but that code actively running, along with everything it needs while running: its own memory space, its current register values, and its execution state.

Why a Process Isn't the Same Thing as a Program

A program is a passive file sitting on disk. A process is that program actively loaded into memory and running - the same program can be launched multiple times, creating multiple separate, independent processes from the exact same underlying program file.

The Five Common Process States

           admitted
New  ------------------->  Ready  <---------------\
                             |                      |
                       scheduler dispatch      interrupt/time-slice expires
                             |                      |
                             v                      |
                          Running  -----------------/
                          /      \
                    I/O or event    exit
                    wait needed        |
                        |              v
                        v          Terminated
                     Waiting
                        |
                 event completes
                        |
                        +----------> back to Ready

What Each State Actually Means

Why Understanding These States Matters

Every scheduling algorithm covered later in this section is really just a set of rules for deciding which Ready process moves into the Running state next - understanding this state diagram is the foundation everything else in process management builds on.