Computer Software

Introduction A set of instructions given to the computer to solve a particular problem is called software Also called computer program Software tells the computer what to do and how to do Hardware operates under the control of given set of instructions Software is developed in computer programming language

Types of Software System Software Application Software

Application Software A program or set of programs that are specially designed to solve the specific problem of users Different kinds of application software Commercial software, scientific software, financial packages, games, multimedia etc Two main categories Custom built software Packaged Software

Custom-Built Software Developed for a particular organization or customer Also known as customize software For example, software developed to maintain the records of students of a particular college

Packaged Software Developed by software development organization for sale to the general public Used to solve some common problems of many people or users Examples Word Processing Software Spreadsheet Software Database Management Software Communication Software Presentation Software Graphics Software

Examples of Graphics Software Computer Aided Design Desktop Publishing Painting Software Image Editing Software Video & Audio editing Software Multimedia Authoring Software Web Page Authoring Software

System Software A program or set of programs that is specially designed to control different operations of the computer system Controls the working of different parts of the computer Enables the other application programs to execute properly Examples: Operating Systems Utility Programs Device Drivers Language Processors

Operating System An operating system is a collection of system programs that controls and coordinates the overall operation of the computer system Also provide the interface between the user and the computer system A computer needs an operating system to do work

Tasks of Operating System Accepts input from input devices Sends output to the output devices Manages the application program in memory Manages the files on the storage devices Manages & controls the I/O devices

Operating System https://en.wikipedia.org/wiki/Process_management_(computing)

Parts of Operating System Resident Part Also known as kernel Contains the critical functions Loaded into the main memory during the booting process of computer Non-Resident Part Loaded into the main memory when required

Examples of Operating System Disk Operating System developed by Microsoft Operating System 2 developed by IBM XENIX developed by Microsoft Windows developed by Microsoft

Operating System Functions When computer is turned on the operating system is loaded into the main memory from the disk Most of the operating system perform the similar functions

Operating System Functions Booting a Computer User-Interface Running Programs Managing Files Memory Management Scheduling Jobs Configuring Devices Establishing Internet Connection Controlling Network Task Management

Booting a Computer The operating system consists of supervisor portion and a set of system programs When the computer is switched on, the supervisor portion of the operating system is loaded in the RAM from the disk The process to start or restart a computer is called booting process Two Types Cold boot Warm Boot

Steps of Booting Process When you turn on the computer, the electric signals make active the processor chip. The processor loads the instructions in ROM. These are computer start up instructions called Firmware. It is BIOS that is automatically activated when the computer is turned on and tests the computer hardware. This type of testing is called Power-On Self Training (POST) After the POST process, the BIOS searches the operating system files called system files on the disk and load these into RAM and then the operating system takes the control of the computer

User Interface User interface means how the user interacts with the computer to perform various tasks User runs the application programs, open the documents, enters the data, print the output report The operating system plays the main role for interfacing between user and computer The hardware devices like keyboard, mouse, monitor are used for interfacing Two main types of user interface Command Line User Interface Graphical User Interface

Running Programs The operating system also provides the interface between the programs and the user Through program, the user access other computer resources There is built in instruction in program known as “system calls” that are used to request the services from the operating system The application program sends the request to the operating system and the operating system gives the result back to the operating system

Running Programs Saving the data from memory in files on the disk Loading the files from disk into memory Sending the document on the printer To copy or move the data from one document to another For the services of hardware To prepare the disk to store data etc

Managing Files The data and programs are stored permanently on the disk for future use The files are stored on the disk by giving a file name The files are placed or stored in folders or directories A folder may contain file or sub folders The operating system maintain a list of these files and folders in the staring area of the disk called FAT File Viewer utility program is used the names of files and sub folders For Example, Windows Explorer

Memory Management Memory unit has very important role for data processing Processor takes data and instructions from RAM during processing The operating system loads the data and programs into RAM and allocates the memory areas and manage these properly When the program is closed, the operating system clears the memory area allocated to that program and its data

Memory Management During data processing some operating system use the hard disk as memory, called virtual memory During processing, operating system transfer some of data from RAM to hard disk and reload when required, called swapping This technique of swapping data between memory and hard disk is called paging Operating systems spends a lot of time in paging process, instead of executing the application software, it is referred to as Thrashing

Scheduling Jobs A job is an activity or operation that a processor performs May be receiving data from input device Sending output to the output device Loading data from disk into RAM Operating system determines the order in which jobs are to be processed First Come First Serve Basis Priority Basis If there are multiple jobs of the same nature, the operating system place the request in buffer, temporary, process called spooling

Configuring Devices The functions of devices attached with the computer are controlled by the special system software called device drivers Device driver tells the operating system how to communicate with a device Each device has its own device driver When you boot a computer, the operating system loads each device driver Usually the operating system has built-in device driver for commonly used input/output devices Operating system automatically install these driver

Establishing Internet Connection Operating System provides means to establish connection between your computer and the ISP (Internet Service Provider) server Some Operating System have built-in program used to access the information on the internet Information downloaded from the internet is managed by the operating system in RAM as well as in disk

Controlling Network Some operating system are specially developed for networking Called Network Operating System (NOS) A network operating system organizes and coordinates multiple users and make it possible to access and share resources on network Overall functions of users are controlled by NOS Creation of account of new user Deletion of user account if required NOS also has security features Require a user name and password to access the network Cannot be accessed by un-authorized persons

Task Management A task is an operating such as storing, printing, calculating etc A computer can perform many tasks at a time Some operating system can handle more than one program at the same time The operating system manage all these tasks Some operating system have single user functionality and can support only one user at a time

Task Management The operating system performs the following tasks: Multi Tasking Multi Programming Multiprocessing Time Sharing Multithreading Virtual Memory Spooling

Types of Operating System In the past, operating system were computer dependent An operating system running on one machine could not be run another different type of machine Three basic categories of operating system are: Personal Computer Operating System Network Operating System Embedded Operating System

Personal Computer Operating System Also called stand alone operating system or single user operating system Used to operate personal computers Examples DOS Mac OS Windows

Network Operating System Supports the network Typically resides on a server and controls the devices or computers connected to the network Examples: Windows NT Server Windows 2000 Server UNIX Solaris Novell’ s Netware

Embedded Operating System Different special electronic devices and handheld computers are also controlled by the operating systems that are stored in the ROM chip Examples: Windows CE Pocket PC 2002 Palm Operating System

Difference between Windows & DOS DOS provides command line Interface, while Windows provides Graphical User Interface DOS is single tasking operating system, While Windows is multi-tasking operating system DOS does not provide plug and play feature, while Windows provide plug and play feature

Utility Programs A software that helps the user to solve the specific problems related to the software and hardware is called utility programs It is system software A large number of utility programs are available for the service of hardware and software Most operating system include various utility programs While others are available on CDs or can be downloaded from the internet

Utility Programs File Viewer File Compression Diagnostic Utility Program Un-Installer Disk Scanner Disk Defragmenter Back up Utility

Device Drivers The programs that operate and control the devices attached to the computer are called device drivers The keyboard, mouse, disk driver, CD-ROM drive, Modem, Printer etc require to install software that tells the computer how to use the device When you purchase a new hardware device, manufacturer of the device also provides you a disk containing a device driver

References Introduction to Information Technology by Riaz Shahid, CM Aslam and Safia Iftikhar The Concepts of Information Technology by Imran Saeed, Ahsan Raza, Tariq Mehmood and Zafar Hussain