To identify the processes in the operating system each process is assigned a process identification number(PID). As Operating System supports multiprogramming, it needs to keep track of all processes. Process Control Block is used to track the process execution status.
Open Source refers to any program whose source code is made available for use or modification as users other developers see fit. Usually, this kind of operating system is developed as a public collaboration and made freely available to everyone. Most of the open-source operating system was released under a license where the copyright holder allows others to study, change as well as distribute software to other people