The SCO OpenServer UNIX operating system is a multiuser, multitasking operating system.
An ``operating system'' is a program that manages the resources of the computer. An operating system sets up a consistent way for programs to request resources, such as time on the processor, or space in memory, from the computer itself. Operating systems look after all the devices attached to the computer, such as printers, modems, disks, and terminals. Another part of an operating system's job is to maintain a filesystem; that is, to set up a consistent way for information to be stored and retrieved.
On a multiuser, multitasking system, several people can do several tasks at once using the same computer.
The term ``the UNIX operating system'' usually refers to the kernel, which is the heart of the operating system. People use a variety of shell programs to communicate with the kernel, which, in turn, communicates with the hardware. The UNIX operating system also includes a wide range of programs that meet the day-to-day needs of computer users and programmers.
Three layers of the UNIX system: kernel, shell, and commands
The UNIX system is called a multiuser operating system because more than one person can use the computer at the same time. In a typical office setup, one computer runs the UNIX operating system and several people share this computer, each using a terminal which is connected to it.
The UNIX system is called a multitasking operating system because each user can do several tasks at once. On a single-tasking operating system, such as DOS, if you type a command that takes a long time for the computer to process, you have to wait for the computer to finish processing before you can continue working. On a UNIX system, you can put commands ``in the background.'' This means you can start working on something else while the computer continues to process your other commands in the background.