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Operating system concept

An operating system is software that manages computer hardware resources and provides common services for computer programs. It acts as an intermediary between users and the computer hardware. The main goals of an operating system are to control allocation of system resources including memory, CPU time, and disk space, provide a platform for execution of programs, make the computer system convenient to use, and use computer hardware efficiently. An operating system separates applications from the hardware they access and manages both software and hardware resources to produce desired results. It primarily functions as a resource manager.

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Operating System Concept Sunawar Khan MBA(IT), MS(CS)
What Is An Operating System? • An Operating System is an interface between user and hardware of a computer system. • An Operating System is a system software which may be viewed as an organized collection of software consisting of procedures for operating a computer and providing an environment for execution of programs. • An Operating System is a control program. • This program controls the execution of user programs to prevent errors and improper use of the computer. • An Operating System is similar to a Government. • An Operating System can be defined as a Resource Manager. • As a resource manager and allocator, the OS will resolve the confliting request for computer resources(CPU time, memory space, files storage space, input/output devices, etc) from various users or programs.
What Is an Operating System? • Separates applications from the hardware they access • Software layer • Manages software and hardware to produce desired results • Operating systems primarily are resource managers • Hardware • Processors • Memory • Input/output devices • Communication devices • Software applications
Goals of An Operating System • A computer’s Operating system is a group of programs designed to serve two basic purposes: • To control the allocation and use of the computing system’s resources among the various users and tasks. • To provide an interface between the computer hardware and the programmer. • To make the computer system convenient to use. • To use the computer hardware in an efficient manner. • provide an environment in which a user may execute programs.
Goals Efficiency Robustness Scalability ExtensibilityPortability Security Protection
Structure of Operating System Application Programs System Programs Software (Operating System) HARDWARE User
Three Elements of OS User Interface • The part of the OS that you interface with. Kernel • The core of the OS. Interacts with the BIOS (at one end), and the UI (at the other end). File Management System • Organizes and manages files.
Physical Devices Microprogramming Machine Language Operating System Compilers Banking System Airline System Editors Command Interpreter Application Programs System Programs Hardware A Computer system consists of Hardware, System Programs and Application Programs How Computer SystemWorks
Physical Devices Integrated circuit chips, wires, power suppliers, cathode ray tube, etc. A Computer system consists of Hardware, System Programs and Application Programs How Computer SystemWorks
Physical Devices Microprogramming Directly controls the physical devices and provides a cleaner interface to the next layer. It interprets the instructions from the above layer and carry out them. A Computer system consists of Hardware, System Programs and Application Programs How Computer SystemWorks
Physical Devices Microprogramming Machine Language Instructions for moving data around the machine, doing arithmetic and comparing values. I/O devices are controlled by loading values into specified device registers. A Computer system consists of Hardware, System Programs and Application Programs How Computer SystemWorks
Physical Devices Microprogramming Machine Language Operating System Major function is to hide all h/w complexity and give the programmer a more convenient set of instructions to work with. A Computer system consists of Hardware, System Programs and Application Programs How Computer SystemWorks
Physical Devices Microprogramming Machine Language Operating System Compliers Editors Command Interpreter The OS runs in kernel mode but the compilers and editors run in user mode. If a user does not like a particular complier, the user is free to write his own but he is not free to write his own disk interrupt handler, which is part of the OS. A Computer system consists of Hardware, System Programs and Application Programs How Computer SystemWorks
Physical Devices Microprogramming Machine Language Operating System Compliers Banking System Airline System Editors Command Interpreter These programs are written by the users to solve their particular problems, such as commercial data processing, engineering calculations, or game playing. A Computer system consists of Hardware, System Programs and Application Programs How Computer SystemWorks
Types of Operating Systems On The Base of Processing Batch Processing OS Time Sharing OS Real Time OS On the Base of User Single User OS Single User Single Tasking Single User Multitasking Multiuser OS Multi programming OS Multitasking OS Multi Processing OS On the Base of Interface Command Line Interface Menu Driven Interface Graphical User Interface
Processing Based OS • Batch Processing OS • Users submit jobs to a central place where these jobs are collected into a batch, and subsequently placed on an input queue at the computer where they will be run. The user has no interaction with the job during its processing. The computer’s response time is the turnaround time- the time from submission of the job until execution is complete, and the results are ready for return to the person who submitted the job. • Time Sharing OS • Computer provides computing services to several or many users concurrently on-line. Various users are sharing the central processor, the memory and other resources of the computer system. The user has full interaction with the program during its execution. • Real Time OS • A RTOS is designed to support execution of tasks within specific wall clock time constraints. Use of RTOS is mostly limited to dedicated applications such as industrial control systems, weapon systems and computer-controlled products. RTOS is managing the resources so that a particular operation executes in precisely the same amount of time every time it occurs.
Multiprogramming Based OS Multitasking Operating System • More than one active user programs to be stored in the main memory. Multiprocessing OS • A computer hardware configuration that includes more than one independent processing unit.
Evolution of OS Major Phases Technical Innovation Operating System Open Shop The idea of OS IBM 701 open shop (1954) Batch Processing Tape batching, First-in, first-out scheduling. BKS system (1961) Multi- programming Processor multiplexing, Indivisible operations, Demand paging, Input/output spooling, Priority scheduling, Remote job entry Atlas supervisor (1961), Exec II system (1966) Timesharing Simultaneous user interaction, On-line file systems Multics file system (1965), Unix (1974) Personal Computing Graphic user interfaces OS 6 (1972) Pilot system (1980) Distributed Systems Remote servers WFS file server (1979) Unix United RPC (1982) 24 Amoeba system (1990)
Booting • Cool Boot • Warm Boot Memory Management • Virtual Memory • Swap File • Thrashing Job Scheduling Device Controlling Accessing Web Monitoring Performance House Keeping Services Function of OS
Functions of Operating System • Memory management • The o/s keeps track of the memory, what parts are in use and by whom. • Process management • The o/s keeps track of processors and the status of processes. It decides who will have a chance to use the processor. • Device management • The o/s keeps track of the devices, channels, control units and decides what is an efficient way to allocate the device. • Information management • O/S keeps track of the information, its location, use, status etc. and decides who gets use of the resources, enforce protection requirement • Protection • An o/s is to protect the user from unauthorized access of his files or data. And also it should protect itself from users • Error Handling • An o/s must respond to errors by taking the appropriate actions.-*
Utility Programs Types • File Manager • ImageViewer • Search Utility • Drive Imaging • Disk Burning • File Compressor • Diagnostic Utility • Personal Computer Maintenance Utility • Disk Scanner • Antivirus • Disk Defragmenter • Backup and Reset Utility • Task Manger Utility • Disk Cleanup • Uninstaller • Task Scheduler Utility • Personal Firewall • Spyware Remover • Adware Remover • File Conversion Utility
•Success Is A Journey Not A Destination. •Sunawar Khan