1. PC-Introduction Latin Word ‘Compute’ means to calculate. Definition : A computer is an electronic device which process or manipulates the data strictly according to the instructions and produces meaningful results efficiently, effectively and reliably. Note : Computer is also known as a ‘faithful idiot’.

2. Computer Vs.Human Being ActivityComputerHuman Being Speed of workingExtremely HighSlow AccuracyExtremely HighVery Low ReliabilityVery HighDecrease with increase in work Ability to think & handle adhoc situation Not availableCan reason heuristically. Solve problems step by step on the basis of past experience. Versatility Highly versatileCan be used for variety of jobs.not versatile.

3. Characteristics of Computers i.Speed ii.Storage iii.Accuracy iv.Versatility v.Automation vi.Diligence vii.Power of remembering viii.No IQ ix.No feeling

4. Computer generations I.First generation(1942-1955) Key characteristics : i.Fastest calculating device of their time. ii.Bulky in size. iii.Highly unreliable. iv.Limited commercial use. v.Commercial production difficult and costly. vi.Difficult to use.

5. II. Second generation(1955-1964) Key characteristics : i.Faster ii.Smaller iii.More reliable iv.Easier to program than previous generation system v.Commercial production was still difficult and costly.

6. III.Third generation (1964-1975) Key characteristics : i.Faster and smaller ii.More reliable iii.Easier and cheaper to produce commercially iv.Easier to use v.Easier to upgrade than previous generation systems vi.Scientific vii.Commercial and interactive on-line applications.

7. IV.Fourth generation(1975-1989) Key characteristics : i.Small, affordable, reliable and easy to use PCs. ii.More powerful and reliable mainframe systems. iii.General purpose machines. iv.Easier to produce commercially.

8. V. Fifth generation(1989-Present) Key characteristics : i.Portable computers ii.More powerful, cheaper, reliable and easier to use desktop machine. iii.Very powerful mainframes iv.Very high uptime due to hot-pluggable components v.General purpose machines vi.Easier to produce commercially.

9. Block Diagram of a Computer ALU MEMORY CONTROL INPUTOUTPUT

10. Components of a computer system Input unit Output unit Memory unit Arithmetic and Logical unit CPU Control unit

11. Functions of Input unit 1.Accepts(or read) instructions and data from outside world. 2.Converts these instructions and data in computer acceptable form. 3.Supplies the converted instructions and data to computer system for further processing.

12. Functions of Output unit 1.Accepts the results produced by the computer, which are in coded form and hence, we can not easily understand them. 2.Convert these coded results to human acceptable(readable) form. 3.Supplies the converted results to outside world.

13. Basic operations performed by a computer 1. Inputting-Process of entering data and instructions. 2. Storing- Saving data and instructions and make them available as and when required. 3. Processing- Performing Arithmetic operations or Logical operations on data to convert them into useful information. 4. Outputting- Producing useful information or results for a user. E.g. printed report or visual display. 5. Controlling- Directing the manner or sequence in which the above operations are performed.

14. Input Devices i.Keyboard ix. Joystick ii.Mouse x. Digital camera iii.Scanner xi. Barcode Reader iv.Magnetic Ink Character Recognition (MICR) v.Optical Mark reader(OMR) xii. Touch Screen vi.Optical Character Recognition(OCR) vii.Digitizing Tablet xiii. Touch pad viii.Trackball xiv. Light pen xv. Speech Input Device

15. Output Devices i.Visual Display Unit or Screen ii. Sound Cards and Speaker iii. Printer