Principal events that cause process creation and process termination?

Answer 1

1. System initialization. When an OS is booted, typically several processes are created.
2. Execution of a process creation system call by a running process. Often a running process will issue system calls to create one or more new processes to help it do its job. Creating new processes is particularly useful when the work to be done can easily be formulated in terms of several related, but otherwise independent interacting processes.
3. A user request to create a new process. In interactive systems, users can start a program by typing a command or (double) clicking an icon.
4. Initiation of a batch job. Here users can submit batch jobs to the system (possibly remotely). When the OS decides that it has the resources to run another job, it creates a new process and runs the next job from the input queue in it.

Answer 2

Process creation is typically initiated by the execution of a "fork" system call within an existing process, which creates a new child process. Process termination often occurs when a process explicitly exits by calling the "exit" system call or encounters an error that causes it to terminate. Other events that can trigger termination include receiving a signal from another process or reaching the end of the program.