1. What is the process?
(1), the process is a dynamic process rather than a static kind
(2), the process is a process of running the program, a static executable program a.out of a running cycle (./a.out from running to the end) is a process.
(3) the process control block PCB (process control block), the kernel data structures used to manage a process.
2, the process ID
(1), the process ID of each process is the system will assign an ID, with previous similar file descriptor.
(2), the correlation function has getpid, getppid, getuid, geteuid, getgid, getegid
3, multi-process scheduling principle
(1), operating systems simultaneously run multiple processes
(2), parallel and serial on micro macroscopically
For single-core operating system, when we see multiple processes running at the same time, when, in fact, multiple processes running in alternating, but time is too short, so we see the human eye is running at the same time
(3), in fact, a modern operating system, the smallest unit of scheduling is the thread rather than process.