Operating Systems

Course: B.Sc-CSSubject: Fundamental Of Information Technology

Unit: 3

Operating System Software• Operating System (OS) – Software that controls the overall operation of a

computer

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What is an operating system (OS)?Operating System Software

Software which manages the overall operation of the computer system including:• hardware (CPU, RAM, I/O)• security• system interface• application interface

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The functions of an operating system

1. Manages and Interacts with Computer Hardware

2. Provides and Manages System Security

3. Provides the System Interface

4. Provides the Interface for Application Software

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1. Manages and Interacts with Computer Hardware

• Manages the CPU- What software programs the

CPU works on and when

• Manages RAM- What is stored in RAM and where it is stored- Virtual memory- OS will send message when RAM is full

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1. Manages and Interacts with Computer Hardware (continued)

• Provides the interface for storage devices and manages how data is stored on those devices- in charge of formatting disks- creates sectors and clusters- creates F.A.T. or V.T.O.C.- sends message when disk is full or there is some other problem with writing data to the disk

- virtual memory - CD-ROM, DVD-ROM - Flash drive

1. Manages and Interacts with Computer Hardware (continued)

• Provides the Interface for Input and Output Devices– keyboard, mouse, printer, – device drivers = software

programs which allow the hardware device to be used by the operating system and by application software

Rick Graziani graziani@cabrillo.edu 7

2. Provides and Manages System Security

Single-user Operating Systems• minimal security• user has full authority

Server Operating Systems• login and password capability• protection of user’s data stored

on the server’s central hard disk drives

• protection and security for software programs

Rick Graziani graziani@cabrillo.edu 8

3. Provides the System Interface

System Interface or shell = the interface between the user and the computer

Command Line Interface (CLI)

• Linux, UNIX, DOS, older OS’s

Graphical User Interface (GUI)

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4. Provides the Interface for Application Software

• Operating systems are software

• Operating systems are designed and developed for a specific CPU or “family of CPUs”– Macintosh OS: Motorola 680xx,

PowerPC Gx, Intel– DOS: Intel CPUs– Windows 9x and XP: Intel

80386, 80486, and Pentium CPUs

– Linux: Intel CPUs– MS NT & 2000: Intel CPUs

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4. Provides the Interface for Application Software (continued)

• Application software is developed for an operating system

MS Word for Windows XP• Windows XP• Intel CPU

MS Word for the Macintosh• Macintosh OS X• Gx CPU or Intel CPU

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Order of Development

1. The CPU

2. Other Hardware Components

3. Operating System Software

4. Application Software12

Types of Operating System

Architecture of Computer System

Hardware

Operating System (OS)

Programming Language (e.g. PASCAL)

Application Programs (e.g. WORD, EXCEL)

Operating System

• a collection of programs which control the resources of a computer system

• written in low-level languages (i.e. machine-dependent)

• an interface between the users and the hardware

• when the computer is on, OS will first load into the main memory

OperatingSystem

Device configurationControls peripheral devices connected to the computer

File managementTransfers files between main memory and secondary storage, manages file folders, allocates the secondary storage space, and provides file protection and recovery

Memory managementAllocates the use of random access memory (RAM) to requesting processes

Interface platformAllows the computer to run other applications

Basic functions of the operating system

Other function of Operating System

• best use of the computer resources• provide a background for user’s programs to

execute• display and deal with errors when it happens• control the selection and operation of the

peripherals• act as a communication link between users• system protection

Common Operating Systems and Their Differences

• Network Operating System– UNIX / Linux / MS Windows2000 Server

• Desktop Operating System– MS Windows 9X/Me / Mac OS / DOS

• Mobile Operating System– Palm OS and Pocket PC

Different Features of Operating System

Type of Operating System

• Batch processing• Real time processing• Time sharing processing

Batch processing

• Jobs, together with input data, are fed into the system in a batch.

• The jobs are then run one after another.• No job can be started until previous job is

completed

Real time processing

• immediate response is needed.

• For example – anti-missile defense system– airplane landing control system– interrupt error in computer system

Time sharing processing

• Each user is given a time slice to interact with the CPU.

• The size of the time slice will depend on the system.

• Each user is served in sequence.

Special Features of OS

• multi-tasking• multi-programming• parallel processing• buffering• spooling

Multi-tasking

• to handle 2 or more programs at the same time from a single user ‘s perception– CPU can only perform one task at a time, however,

it runs so fast that 2 or more jobs seem to execute at the same time

Multi-programming

• 2 or more programs store in the main memory at the same time

• when one job reeds to wait (e.g. I/O operation), CPU switch to another job to execute

• when the first job finishes waiting, CPU will get back the first job to execute

Parallel Processing

• use 2 or more CPUs to handle jobs• computer networking

Job 1 Job 2

Job 3

Job 4

Job 1

Job 2

Job 3

Job 4

CPU 1 CPU 2 CPU 1

time time

without multiprocessing

with multiprocessing

Buffering

• A temporary storage area (buffers) to read data from input device or send data to the output device

• keep CPU busy– because I/O operation is slow

Reference

Book Reference1. Operating System Concepts by Abraham Silberschatz,

Peter B. Galvin, Greb Gagne2. Operating System Concepts by James Lautor

Peterson, Abrahamautor Silbeschatz3. Database System Concepts by Abraham Silberschatz,

Henry F. Korth, S.SudarshanImage Reference4. https://www.google.co.in/search?q=database+Manage

ment+system+books&hl=en-IN&biw=1517&bih=714&tbm=isch&source=lnms&sa=X&ei=9MCjVLPGIdTmuQTen4HQCQ&ved=0CAYQ_AUoAQ&dpr=0.9#hl=en-IN&tbm=isch&q=database+Management+system

5. https://www.google.co.in/search?q=database+Management+system+books&hl=en-IN&biw=1517&bih=714&tbm=isch&source=lnms&sa=X&ei=9MCjVLPGIdTmuQTen4HQCQ&ved=0CAYQ_AUoAQ&dpr=0.9#hl=en-IN&tbm=isch&q=operating+system