Operating System

Operating System

Operating System • A special system software that acts as an intermediary between a user of a computer and the computer hardware. • Provides an environment in which the user can execute programs/applications in a convenient and efficient manner. User 

Operating System

Hardware Examples of OS: Windows, MS-DOS, Linux, Unix

Operating System. Thus the main goals for an Operating system are: • Make computer convenient to use (hides Hardware details) • Utilize resources in efficient manner

Operating System User Application Software

Operating System

Computer hardware

Functions of O/S 1. 2. 3. 4. 5. 6. 7. 8. 9.

Pro Process Management Memo emory Managemen ementt Deadlock Ha Handling File Management I/O Management Pro Protecti ectio on & Sec Securit urity y Job scheduling Interp Interpret retati ation on of comman commands ds and ins instr truct uction ions. s. Co-o Co-ord rdin inat atio ion n of comp compil iler ers s and, and, assem assembl bler er,, programs and other s/w of computer system.

Functions of O/S 10. Production Production of error messages. messages. 11. Maintenance of internal time clock and log system usage for all users. 12. Provides easy communication between the computer system and users. 13. Resource Allocator 14.Intermediary 15. Executes Executes application application software software 16. Memory Memory manageme management nt 17.CPU Scheduling

CATEGORIES OF OPERATING SYSTEMS Operating systems can be categorised by the number of users they support as well as by their level of sophistication.  Three categories are broadly recognized:1. Desktop O/S: • Designed to support a single user or a small work group of users. 2. Departmental O/S: • Supports from a few dozen to a few hundred users.

CATEGORIES OF OPERATING SYSTEMS 3. Enterprise O/S: • Generally supports thousands of users and transactions simultaneously. • Offers the greatest functionality, followed by departmental operating systems, and then desktop operating systems. •  The user interface is the least sophisticated on enterprise operating systems.

Desktop Operating System

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Desktop Operating System

Supports a single user or a small s mall group of users. Some Some exam exampl ples es of the the oper operat atin ing g sys syste tems ms in thi this category are:-

1. MS-DOS: • One One of of tthe he orig origin inal al oper operat atin ing g sys syste tems ms for for the the IBM IBM PC and its clones. • A non non-g -gra raph phic ical al,, lin line e ori orien ente ted, d, comm comman andd-dr driv iven en operating system, with a relatively simple interface but not a friendly user interface. • It was was not not capa capabl ble e of mult multit itas aski king ng.. • It has has now now been been almo almost st tota totall lly y repl replac aced ed by GUI GUI products such as Windows 95, Windows 98, Windows 2000 and Windows XP.

Desktop Operating System 2. Windows 3. 3.1 • It is a transition windowing system between MS-DOS and Windows95, Windows 98 and Windows 2000. • It is not actually an operating system, but a GUI that operates with, and extends the capabilities of MS-DOS

Desktop Operating System 3. Windows 95 •  The first of a series of products in the Windows operating systems that provides a GUI by using icons to provide instant access to common tasks. • It is a 32-bit operating system that features multitasking, networking, and Internet integration capabilities. • It also offers plug-and-play capabilities by enabling the operating system to recognize new hardware and install the necessary software (device drivers) automatically.

Desktop Operating System 4. Windows 98 • Offered minor refinements, bug fixes, and enhancements to windows 95. 5. Windows NT • An operating system for high-end desktops and workstations. • It provides the same GUI as Windows 95, 98, and 2000. • Has more powerful multitasking, and memory management capabilities. • It is popular in networked systems in business organizations.

Desktop Operating System 6. Windows 2000 • Microsoft changed the name of the upgrade of  Windows NT 5.0 to Windows 2000. •  This operating system has added security features. • Runs on multiprocessor computers. • Offers added Internet and Intranet functionality. 7. Wind Window ows s CE (Com (Compa pact ct Edit Editio ion) n) • Is a 32-bit operating system designed for hand-held PCs, and wireless communication devices.

Desktop Operating System 8. IBM’ IBM’s s OS/ OS/2 2 Ope Opera rati ting ng Syst System em • A 32-bit operating system that supports multitasking, and supports networked applications. 9. Macintosh Operating System • For Apple Macintosh microcomputers. • Is a 32-bit operating system that features multitasking and powerful graphics capabilities.

Desktop Operating System 10.Unix • Provides many sophisticated desktop features, including multiprocessing and multitasking techniques. • Is valuable to business organizations because it can be used on many different sizes of  computers ( different hardware: non Intel and Intel processors). • Was popularized by Sun Microsystems.

Desktop Operating System 11. 11. Linu Linux x • A powerful version of Unix . • Completely free of charge. • It offers multitasking, virtual memory management, and  TCP/IP networking. • Originally written by Linus Tovalds at the University of  Helsinki in 1991. • He then released the source code to the world. • Like Unix, it runs on multiple hardware platforms. • Is becoming widely used by Internet service providers. •  The clearinghouse for Linux information on the Internet may be found at www.linuxhq.com

Desktop Operating System 12. Java Operating Operating System System •

Is designed for hand-held products and network computers.

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Sun’s java operating system executes programs written in Java language without the need for a traditional operating system.

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It is designed for Internet and Intranet applications and embedded devices.

Departmental Server Operating Systems

Departmental Server Operating Systems

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 The major departmental server operating systems include:Unix Windows NT server IBM’s OS/2 Warp Server Novell NetWare IBM’s OS/400

Departmental Server Operating Systems Although some of these are also desktop OS, all can serve as departmental server OS because of their:• Strong scalability • Reliability • Backup • Security26 • Fault tolerance • Multitasking • Multiprocessing •  TCP/IP networking • Network management

Enterprise Enterprise Operating Systems

Enterprise Operating Systems  The major enterprise operating systems include: • • • •

IBM’s MVS (Multiple Virtual Storage) IBM’s VM (Virtual Machine) IBM’s VSE (Virtual Storage Extended) Digital Open VMS (Virtual Machine System)

Enterprise Operating Systems Enterprise operating systems support: • • • •

Secure electronic commerce Multiple concurrent users Large (terabyte) databases Millions of transactions per day.

Types of O/S • Multitasking • Multiprogramming •  Time sharing • Multiprocessing

MULTITASKING O/S • Executing more than one task concurrently. • Execution of two or more tasks/programs by one user concurrently on the same computer with one central processor. • For example, the user may be running one program and simultaneously listening to a music file.

Multiprogramming Operating System • Refers to concurrent execution of different users’ programs on a machine with a single processor. • It is the execution of two or more programs concurrently on a multi-user operating system. •  The processor spends a certain amount of time executing each user’s program. As the processor works much faster, faste r, it seems as though all the programs are being run at the t he same time.

Time Sharing Operating System • Round-Robin processing of programs for several users. • A single computer processes the tasks of  several users at different locations based on the concept of time slicing between the users.

Multiprocessing Operating System • Simultaneous processing of two or more programs by multiple computers or processors linked together to perform work simultaneously. •  This can involve processing of instructions from different programs or different instructions within the same program simultaneously. • Implemented using concepts of parallel processing.

Real Time Operating System • an operating system that guarantees a certain capability within a specified time constraint • Such applications include embedded systems and scientific research equipment. • Provide Provides s faciliti facilities es which, which, if used used properly properly,, guarante guarantee e deadlines can be met. • Uses specialized specialized schedu scheduling ling algorithms algorithms in order order to to provide provide the real-time developer with the tools necessary to produce deterministic behavior in the final system. • An RTOS is valued more for how quickly and/or predictably it can respond to a particular event • An early example of a large-scale real-time operating system was the so-called "control program" developed by American Airlines and IBM for the Sabre Airline Reservations System.