What is computer virus how can we protect our computer from it

Virus:
A computer virus is a software program which performs a malicious function that infects the other programs or damages the disk. This virus replicates itself within a computer system.

Function of viruses:

1. It infects the other programs. 
2. It damages the disk it destroy the data of the disk. 
3. Sometimes it makes the PC unusable. 
4. It increases he file size of the file on the disks, but not effect its functioning. 

Protection From Viruses: 

1. Never boot you system, it ensure that the floppy used for booting a system is free from virus. 
2. A system booting disk must be kept write protected. 
3. Avoid using .com, .sys or exe files not know to you. 
4. Avoid from the users of pirated softwares. 
5. Always use only virus free programs and disks. 

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Describe a CPU and its different units with the help of block diagram

CPU:
Central processing unit is the brain of computer system. We use to control all input and output connections inside and outside of the computer to produce correct answer for their users it conrols and supervises all the units in a computer. It takes information from the input unit an dform the memory, and uses it according to the instruction already given to the computer from functional point of view CPU consist of three parts.

1. Arithmetic and Logic Unit(ALU):
2. Control Unit(CU)
3. Memory Unit(MU)

Arithmetic and Logic Unit(ALU):

The ALU in any microprocessor which provides calculations including additions, subtraction, multiplication and division. It can also performs logical operations like comparing two numbers to logical operations like comparing two numbers to see which number is greater than, less than or equal to another number. The ALU performs million of calculations and comparision at  a very high speed. 

Control Unit(CU):

The Control unit acts like a traffic police man controlling the movements of vehicles on the road, the conrol unit directs and co-ordinates the entire computer system. Its function controlling the input/output units and the arithmetical/logical operation of the CPU, and transferring data to and front storage, within given design limits. The unit direct the system according to the procedures designed by its human operators and programmers. 

Memory Units:

Memory units is the place where the computer program and data are stored during processing. It is the area through which all the data which is input or output of the CPU must pass. It is monitored by CU, which keeps tracks of every thing in the storage. It is a random access device, which consist of thousands upon thousands of storage location each of which can directly reached by CU. Each storage location is distinguish by the address. Memory unit consist of two parts namely. 

1. ROM (read only memory)
2. RAM(random access memory)

ROM: 

Rom is a part of memory unit it contains permanently stored information. When the power is switched off. ROM does not wash away or available to a computer to read and process but not to be changed is kept on ROM. This information is stored on small pieces of memory chips, before the computer isd assembled. 

RAM: 

This part of memory consists of blank chips  and hence the computer can use it to store and retrieve (write and read) information during its processing. The information stored in RAM is volatile i.e, when the compter is shutdown or power failure the information or data stored is lost. 

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List three popular microcomputer spreadsheed packages

The three popular microcomputer are spreadsheet packages: 

1. Lotus 1-2-3
2. Super Calc
3. Microsoft Excel

Lotus 1-2-3

Lotus became almost synonymous with the word spread sheet. Ever since 1-2-3 was introduced in 1982, it has been the spreadsheet program against which all others are compared. This program not only has one of the most powerful spreadsheets in the business, it also includes graphics and data management capabilities. These three major components gives 1-2-3 its name. Lotus 1-2-3 is still by far the most popular spread sheet program for IBM compatibles. It has an especially loyal following in corporate and business markets. 

Super Calc: 

Super calc is an old spread sheet package. Its one of the few programs that was originally released before lotus 1-2-3, yet still survives. Now sold by computer associates international, supercalc began as a  spreadsheet program for computers running under, the CP/M operating system. When IBM introduced its personal computers, super calc was adapted to run on it soon, supercalc 2 and super calc 3 were introduced. Super Calc 2 had improved formatting and macro capabilities, while super calc 3 included graphics and data management. The latest prgram for IBM -Capabilites that can easily hold its won against the like of lotus 1-2-3. Although not a popular as 1-2-3 super calc 5 is a fine product with a substantial following of fiercely loyal users. 

Microsoft Excel: 

Microsoft Excel is a flexible package has become the top selling spreadsheet program. When Microsoft introduced an IBM compatible version of Excel in 1987. PC magazine declared it to be "unquestionably the most powerful PC spread sheet you can buy". It has a graphics interface that makes extensive use of pull down menus, windows and a mouse. Like lotus 1-2-3. Excel Also offers data management, but its graphic abilities are more advanced and easier to use. Microsoft arguably the leading microcomputer software developer, certainly has the technical know-  how and marketing survey so that excel can be a strong competitor of the entrenched lotus 1-2-3.

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List thee popular microcomputer word processing packages

The three popular microcomputer word processing packages are: 

1. Word Star
2. Word Perfect
3. Ms Word

Word Star:

Word Star, from Micro Pro International Corporation, is one of the best known, most long- lived micro computer application packages. Originally introduced in mid 1979 word star become the most popular program for early 8-bit microcomputers running under the CP/M (conrol program for Micro computers) operating system. Soon Apple II Computers, equipped with CP/M circuit boards, also began running word star, finally when the IBM personal computer became a hit, Micro Pro released a version of Word Star to run under PC and MS-Dos. It has been estimated that more than three millions copies of word star has been sold so far. 

Word star si an interesting phenomenon. Despite its immense popularity, reviewers and circuit have breated it as poorly designed, old fashioned, difficult to use and slow. However the most  recent version (release 7) of this venerable package is much faster, much easier to use and offered many advanced word processing features. Thes include pull down menus, context sensitive online help, automatic paragraph, reformatting, mail merge, a index generation, an undo command, macros, character formatting, proportional spacing and math functions. 

Word Perfect:

According to sales figures from retail computer stores word perfect, from word perfect corporation remained best selling word processing package till 1997. Since its introduction in October 1982. Word Perfect has won the highest praise from both reviewers and users like. A rich set of powerful new features seems to be added with every release. Versions have been developed to run on many different machines including IBM, Apple II, Apple Macintosh, Commodore Amiga, Atari ST, and Digital micro VAX computers. The current versions of word perfect includes many of the advanced word processing features. 

Microsoft Word (MS-Word):

Microsoft word is a state of the art word processing package for both IBM and Apple computers first introduced in April 1983 and its subsequent version especially Word 97 and Word 2000 became the program of choice for many people with laser printers. World is often used with a graphics display and a mouse. Like word perfect, MS Word include many of the advanced features. 

Word occupies a unique place as the word processing package most often used in desktop publishing systems. Its graphics interface, along with advanced printing capabilities make ;word ideal for this purpose. Word works with a wide range of printers and it is especially adept at driving laser printers. Backed by the most likely will remain one of the leading word processing packages for a long time to come.

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List the basic functions every word processing packages performs

Basic Functions of Word Processing:

The ultimate purpose of nay word processor is the preparation of documents different types of word processors approach this task in different ways. Some programs are relatively simple designed with the novice or occasional user in mind. Other packages are powerful systems that provide more features than most people even learn, let alone routinely, use perhaps the most apparent difference between various word processing packages involves their user interfaces. Some primarily use various interfaces. Some primarily use commands, while other rely more on menus. Some use the keyboard to mouse finally, some are limited to text displays, while others can utilize graphics to produce various type faces and incorporate figures. 

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What is a default printer, how would you change a default printer

Default Printer:

While you may have more than one printer installed on you computer, only one of these printer can be defined as you default printer, although you can change this default setting at any time. When a printer is set as default it is the printer that is automatically selected each time you print a document. 

You can easily tell which printer is set as the default by looking at the printer icons found within the printer folder. The default printer has a check mark in the upper left portion of its icon. When you install the first printer, on your computer, it is automatically installed as the default printer. Unless you change the default setting, the first printer you install on your computer remains as the default, even if you later add additional printers to the printers folder. If you want to select a different printer as the default, right - click on that printers icon in the printer folder and  choose set as default. The check mark moves to the selected printers icon, and that printer is now set as the default printer. 

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Define file management system?

File Management:

An important part of a computer's operating system is the file management system.  A file may be a document created in word, excel, or other software, or it may be an executable file. The file management part of an operating system has four basic functions.

1. To allocate space on the storage device to hod each file stored, and to de-allocate space when a file is deleted. 
2. To keep track of the allocation units occupied by each file, files may be split over several allocation units, not necessary constigous. A file may initially occupy one unit of 512 bytes, and then when updated by a user, need extra space which may have to be found some where else on the disk. 
3. To control file access rights and permissions. 
4. To map logical file addresses to physical disk addresses, for example a physical drive may be split into several  logical drives C, D, E, F and G. 

Files containing programs and data are located secondary-storage devices. The operating system records the storage location of all files. If you move, rename, or delete a file, the operating system manages such changes and help you locate and gain access to it for example, you can copy, or duplicate, files and programs from one disk to another. You can back up, or make duplicate copy of the contents of a disk. You can erase or remove from a disk  any files or programs that are no-longer useful. You can rename, or give new file names to the files on a disk. 

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Name four types of icons in the windows graphical environment?

Ans: Icons: 

        Icons, the  graphical representation of a windows element, play a mojor role in a windows. Commonly used Icons include application icons, shortcut icons, document and disk drive icons. 

       Applications Icons: 

         An active application  window can be minimized to a button on the  taks bar, there by making it inactive. The application icon, usually a graphic showing software packages logo, is positioned on the button. Point and click(or double-click in windows 95)  on the button or icon to restore the window and the application to active status. 

       Shorcut icons: 

       A shortcut icon to any application, document, or printer can be positioned on the desktop in a folder or on a shortcut bar. The shortcut icon has an arrow in its lower left corner, shorcut are clicked(or double-clicked in windows 95) to begin an application. 

Document Icons: 

The active document window, which is a window which is a application window, an be minimized to a document icon within an applicaiton's work space. Point and click on the document icon to restore the document window. 

Disk-Drive icons: 

The disk drive icons graphically represent several disk-drive options, floppy, hard network (hard), removeable disk(fir exanokem zip disk drive) and CD-ROM(including DVD and CD-RW). The floppy (A), Hard Disk (C, D and E) and CD-ROMs(F and G) icons reemble the faceplates of the disk drivers or show the type of storage media. Typically. PCs have only one or two floppy drivers, assigned to A and B.

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What do you mean by computer Ethics?

Ans: Compute Ethics: 

              Computes pose major ethical problems for all users- governement, clerks, business executives, doctors, supervisors, students and hobbyists. In addition to any laws the exist, computer ethics are needed a standared of behavior for computer use by individuals and organizations. This problem has long concerned computer professionals, who have observed the increasing misuse of computers for  example, there are count less incidents in which someone copies software for a friend, or an employee marks personal use of a company computer during off hours. One might say that there is no loss to the software company because the friend would not have purchased the software anyway, or that the company lost nothing because its computer would have been sitting idle. A code of ethics provides a way of self regulating conduct when the laur or situation doesn't indicate a clear course of action. 

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What is data encryption used for?

Ans: Many data thieves do their work without breaking into computers systems, they intercept message as they travel between computers on networks. Passwords are of little use for hiding electronic mail messages when they are travelling through phone lines or internet gateways still scientific in the name of security. Many networks secure while allowing communication with the rest of the internet. The technical dtails of firwalls vary considerably, but they are all designed  to serve the same function to ground against and unauthorized access to an internal network. In effect, a firewall is a gateway with a lock- the lock gate is opened only for information packets that pass one or more security inspections. 

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