Most of the Unix/Linux operating systems have added a /proc directory to their filesystems. The /proc directory contains information about the current running processes in active RAM. This makes access and management of processes easier and more uniform. This becomes highly important when writing applications that utilize interprocess communication (IPC). The idea behind the /proc directory was to create files that represented processes. Information such as Process IDs (PIDs), environment and user information are stored in /proc.
On Sun Solaris platforms, /proc is actually stored in active RAM and vanishes when the system is shut down.