Introduction to Operating Systems
Every computer comes with an operating system; it is the most important piece of software on a computer and it cannot run without it. It is analogous to the central nervous system of a human being; if human beings did have a functioning central nervous system, their bodies could not perform conscious and unconscious tasks on a daily basis such as breathing, walking eating, etc.
Operating systems control all the devices in a computer by means of software. Consequently, devices can be changed, patches can be added and security updates applied. This facility enables changes to be made to computer systems, eliminating the need to purchase a new one every time a change needs to be made to the system.
At the most basic level, an operating system manages the hardware and software resources of a computer and its peripherals. These resources include the processor, memory, disk space, the mouse and keyboard, and an attached printer. It also provides a stable and consistent means for applications to interact with the hardware without having to know the details of the hardware device.
During the standard use of a computer, various programs and input devices compete for the use of the central processing unit and request memory, storage and input and output for their own purposes. The role of the operating system is to insure that each application running gets the resources it needs on an equal basis while managing the used resources effectively and to their greatest capacity.
A consistent application interface is required if more than one computer is using the operating system. These consistent application interfaces, known as APIs, or application program interfaces, allow portability of applications, even if hardware configurations of the computers are different. They also enable operating systems to be sufficiently flexible to handle hardware from different manufacturers in almost any conceivable combination.
There are considered to be four categories of operating systems based on the types of computers they control and the applications they support.
Real time operating systems were developed to control machinery, scientific instruments and industrial systems. The primary function of a real time operating system is to manage the resources of a specific component so that a particular operation is executed exactly the same way every time. Real time operating systems typically are contained in sealed boxes, having little user interface and end-user capabilities.
Single use, single task operating systems enable a computer to do one application at a time. Mobile devices, such as cell phones and personal digital assistants tend to have this operating system installed.
Single user, multi-tasking operating systems enable a single user to run several applications at a time on a single computer.
Multi-user operating systems enable many users to employ the resources of a single computer simultaneously. This type of operating system must insure that resource usage is balanced, so one user does not affect the ability of others to get their tasks completed.