The Operating System is a piece of software that is being advanced daily in the Information Technology world today. There are many operating systems to choose from but below four specific operating system are compared. Process Management, File Management, Memory Management, and Security are going to be compared between Windows, Linux, UNIX, and Mac operating systems. Every operating system is different and is interesting to see how every piece of software has the same outcome but has different procedures in between. Process management is defined as how the OS manages multiple programs running at the same time. A thread is a feature of an OS that enables parallel processing within a single process. UNIX, Windows, and Mach are all multitasking systems that support both processes and threads. They can be compared in several respects with regard to the process management features.
When executing a program on UNIX, the system creates an environment for that program. In this setting there is everything needed to execute that program. The OS tracks processes though a five digit number Recognized as the Process ID. Each process has its own unique PID. PID’s ultimately repeat because all the probable numbers are used, and the next PID repeats the system again. At any time, no two Processes with the same PID occur in the system, because it is the PID that UNIX uses to track its processes.
Each UNIX process has two ID numbers. The PID or process ID, and PPID or Parent process ID. Each user process in the system has a PPID. Normally, when a child process is killed, the parent process is told by a SIGCHLD signal. Then the parent can do another task, or restart a new process as needed. When a process is killed, a process listing may still show the process with Z stats. This is a zombie, or obsolete process. The process is dead and not being used. These processes have finished the execution but still have an entry in the process table.
Daemons are system related background processes that often run with the consent of root and service requests from other processes. A daemon process has no controlling terminal. It cannot open DEV, or TTY. A daemon is just a process that runs in the background; usually waiting for something to happen that is capable of working with it.
For windows every process contains one or more threads, and the Windows thread is the basic executable unit. Threads are planned on the basis of the usual factors: availability of resources such as CPUs and physical memory, priority, fairness, and so on. Windows has supported symmetric multiprocessing since NT4, so threads can be assigned to separate processors within a system.