Process Creation: A Little More Detail

One mystery that we should unmask a bit is how programs are transformed into processes. Specifically, how does the OS get a program up and running? How does process creation actually work?

Transforming a program into a process

The first thing that the OS must do to run a program is to load its code and any static data (e.g., initialized variables) into memory, into the address space of the process. Programs initially reside on disk (or, in some modern systems, flash-based SSDs) in some kind of executable format; thus, the process of loading a program and static data into memory requires the OS to read those bytes from disk and place them in memory somewhere (as shown in the figure below).