An operating system is a program that manages all the other programs on a computer after being initially loaded into a computer by a boot program. All the other programs are known as applications, and they use the operating system by making requests for the use of services through the defined application program interface. The operating system performs certain tasks for these applications, such as; handling input and output from the attached hardware devices such as printers, hard disks and dial up ports,  dividing up programs so that they can run on more than one processor at a time, sending messages to each interactive user or application about operation status, and errors that may have occurred, and determining what applications should be allowed to run at what times, and for how long so that other applications have a fair turn.
     There are many examples of operating systems such as; Linux, Unix, VMS, Windows 2000, AIX, and z/OS.  All computer usage, both software and hardware require an operating system. Most operating systems fall into one of the following categories; multi-processing, which refers to an operating system that is capable of supporting and utilizing more than one computer processor, GUI, which is short for graphical user interface, and is a system that uses icons and various graphics, and is navigable by the use of a computer mouse, multi-user, which is a system that allows for more than one user at a time or at different times, multi-threading, which are operating systems that allow different parts of software to run at the same time, and finally, multi-tasking, which is an operating system that allows multiple software processes to run concurrently.
     The purpose of any good operating system is to control and effectively organize your hardware and software so that the computer can be predictable, but able to be flexible as well. Without an operating system, the computer is a useless piece of equipment. Having an operating system ensures that, even with a unique computer, the applications will continue to run and be managed effectively while updates and hardware upgrades are being installed. Today’s operating systems can support thousands of disk drives, peripherals, and printers in any combination, and at any amount without any problems.
    The operating systems jobs fall into six general categories; user interface, storage management, application interface, device management, processor management, and memory management.  These six tasks define what the sole purpose of all operating systems basically is. With the operating systems handling the hardware and software resources of a system, it would something like this. With a cell phone, the operating system handles all the applications, such as the; phone dialer, address book, the screen, battery, and the network connections. With a laptop computer, the operating system is in charge of the disk space, memory, processor, and other functions. One challenge that developers face in today’s ever technologically growing world, is the need to keep operating systems able to handle all the new information and hardware that is constantly being developed.