Final answer:
During Unix process creation, the fork() system call creates a new process, then exec() system calls replace the process memory space with a new program. The setuid() function can set the new process's user ID, and exit() is called upon process termination.
Step-by-step explanation:
In Unix-based operating systems, process creation is a fundamental operation. The primary system call used for creating processes is fork(), which initiates a new process that is an exact duplicate of the calling process, but with a new unique process ID. Following the fork, a exec() family of system calls can be used to replace the process's memory space with a new program. The new process also inherits several attributes such as environment variables and file descriptors from the calling process.
Another function involved in process creation is setuid(), which sets the process's user ID, providing the new process with permissions tied to that user ID. Finally, exit() is used when a process ends, performing clean-up operations such as freeing memory and closing files.