INTRODUCTION TO OPERATING SYSTEMS
OVERVIEW
Without its software, a computer is basically a useless lump of metal. With its software a computer can store, process and retrieve information; display multimedia documents; search the internet and engage in other valuable activities. This fundamental software is called the operating system which controls all the computer’s resources and provides the base upon which the application programs can be written.
A modern computer system consists of one or more processors, main memory, disks, printers, network interfaces and input/output devices all of which need to be managed.
What is an OS?
OS as an extended machine/virtual machine
The program that hides the truth about hardware from the programmer and presents a nice, simple view of named files that can be read and written is, of course, the operating system. Just as the operating system shields the programmer from disk hardware and presents a simple file-oriented interface, it also conceals a lot of unpleasant business concerning interrupts, timers, memory management and other low-level features.
Operating System as a resource manager
The operating system is there to manage all pieces of a complex system. Modern computers consist of processors, memories, timers, disks, mice, network interfaces, laser printers and a wide variety of other devices. In the alternative view, the job of the operating system is to provide for an orderly and controlled allocation of the processors, memories and I/O devices among the various programs competing for them.
Summary
A computer’s operating system is its most important program. It is considered the backbone of a computer, managing both software and hardware resources. Operating systems are responsible for everything from the control and allocation of memory to recognizing input from external devices and transmitting output to computer displays. They also manage files on computer hard drives and control peripherals, like printers and scanners.
A multiuser operating system enables multiple users to run programs simultaneously. This type of operating system may be used for just a few people or hundreds of them. In fact, there are some operating systems that are used to allow thousands of people to run programs at the same time.
A multiprocessing operating system allows a program to run on more than one central processing unit (CPU) at a time. This can come in very handy in some work environments, at schools, and even for some home-computing situations.
Multitasking operating systems work a little differently; they make it possible to run more than one program at a time.
Multithreading operating systems are even more different, allowing varied parts of one program to be used simultaneously.
Real-time operating systems are designed to allow computers to process and respond to input instantly. Usually, general-purpose operating systems, such as disk operating system (DOS), are not considered real time, as they may require seconds or minutes to respond to input. Real-time operating systems are typically used when computers must react to the consistent input of information without delay. For example, real-time operating systems may be used in navigation.
Components of the operating system
The operating system comprises a set of software packages that can be used to manage interactions with the hardware. The following elements are generally included in this set of software:
- The kernel, which represents the operating system’s basic functions such as management of memory, processes, files, main inputs/outputs and communication functionalities.
- The shell, allowing communication with the operating system via a control language, letting the user control the peripherals without knowing the characteristics of the hardware used, management of physical addresses, etc.
- The file system, allowing files to be recorded in a tree structure.
Roles of the operating system
The operating system has various roles:
- Management of the processor: the operating system is responsible for managing allocation of the processor between the different programs using a scheduling algorithm. The type of scheduler is totally dependent on the operating system, according to the desired objective.
- Management of the random access memory: the operating system is responsible for managing the memory space allocated to each application and, where relevant, to each user. If there is insufficient physical memory, the operating system can create a memory zone on the hard drive, known as “virtual memory“. The virtual memory lets you run applications requiring more memory than there is available RAM on the system. However, this memory is a great deal slower.
- Management of input/output: the operating system allows unification and control of access of programs to material resources via drivers (also known as peripheral administrators or input/output administrators).
- Management of execution of applications: the operating system is responsible for smooth execution of applications by allocating the resources required for them to operate. This means an application that is not responding correctly can be “killed”.
- Management of authorizations: the operating system is responsible for security relating to execution of programs by guaranteeing that the resources are used only by programs and users with the relevant authorizations.
- File management: the operating system manages reading and writing in the file system and the user and application file access authorizations.
- Information management: the operating system provides a certain number of indicators that can be used to diagnose the correct operation of the machine.
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