CLASS IX COMPUTER APPLICATIONS Textbook: DINESH Super Simplified Computer Applications BY Dr. Vipan Arora UNIT – 1 BASICS OF INFORMATION TECHNOLOGY PART – 1 (DETAILED EXPLANATION-NOTES)

COMPUTER SYSTEM

What is a Computer? A Computer is an automatic electronic, calculating device which can process a given input in a prescribed manner to produce a desired output. CHARACTERISTICS OF COMPUTERS 1. Speed: Computers work at an enormous speed. 2. Accuracy: If the computer is given correct data and instructions, then only it will return an accurate result. 3. Diligence: The computer neither gets tired nor bored doing the same task as many number of times as you want. 4. Versatility: Computers are capable of doing varied types of jobs. 5. Enormous Storage Capacity: Computers can store a large amount of information and data in their memory. Computer Hardware: Hardware represents the physical and tangible components of a computer, i.e. the components that can be seen and touched. Examples of Hardware are the following −

• Input devices − keyboard, mouse, etc.

• Output devices − printer, monitor, etc.

• Secondary storage devices − Hard disk, CD, DVD, etc.

• Internal components − CPU, motherboard, RAM, etc.

Computer Software: Software is a set of programs, which is designed to perform a well-defined function. A program is a sequence of instructions written to solve a particular problem. Components of a Computer System Every computer system has the following three basic components: 1. Input unit 2. Central processing unit 3. Output unit

Input Unit These components help users enter data and commands into a computer system. Central Processing Unit (CPU) After receiving data and commands from users, CPU processes it according to the instructions provided. The CPU further uses these three elements: a) Memory Unit Once a user enters data using input devices, the computer system stores this data in its memory unit. b) Arithmetic and Logic Unit This part of the CPU performs arithmetic operations and logical functions. c) Control Unit This unit is the backbone of computers. It is responsible for coordinating tasks between all components of a computer system. Output Unit The output unit displays the information to users.

Storage devices A storage device refers to a hardware used to store information permanently or temporarily. The device can be external or internal to a computer. TYPES OF MEMORY 1. Primary Memory / Volatile Memory. 2. Secondary Memory / Non-Volatile Memory.

Types of Storage Devices There are two different types of storage devices:

Primary Storage Device Secondary Storage Device

Smaller Larger

Temporary Permanent

Internal Internal / External

RAM, Cache Memory Hard disk, Compact Disk Drive, USB storage device

Examples of Storage Device Magnetic Storage Device – one of the most popular types of storage used.

Hard drive – An internal hard drive is the main storage device in a computer. An external hard drive is also known as a removable hard drive. It is used to store portable data and backups.

CD-ROM disc – An optical storage device that is read-only or cannot be modified nor deleted.

DVD, in full digital video disc or digital versatile disc, type of optical disc used for data storage and as a platform for multimedia.

Memory stick – A memory card that is removable.

USB flash drive, jump drive or thumb drive – A small, portable storage device connected through the USB port.

INPUT DEVICES--- Keyboard Keyboard is the most common and very popular input device which helps to input data to the computer. The layout of the keyboard is like that of traditional typewriter, although there are some additional keys provided for performing additional functions.

Mouse Mouse is the most popular pointing device. It is a very famous cursor-control device having a small palm-size box with a round ball at its base, which senses the movement of the mouse and sends corresponding signals to the CPU.

Scanner Scanner is an input device, which works more like a photocopy machine. It is used when some information is available on paper and it is to be transferred to the hard disk of the computer.

Web camera A webcam is a hardware camera and input device that connects to a computer and the Internet and captures either still pictures or motion video of a user.

OUTPUT DEVICES Monitors Monitors, commonly called as Visual Display Unit (VDU), are the main output device of a computer. It forms images from tiny dots, called pixels.

Printers Printer is an output device, which is used to print information on paper.

There are two types of printers − • Impact Printers • Non-Impact Printers

ASSIGNMENT QUESTIONS Note: Answers to be written in the register. 1. What do you mean by a Computer? 2. Write the function of Input Unit. 3. Differentiate between RAM and ROM. 4. Write the full forms of the following: a) CPU b) ALU c) RAM d) ROM 5. What is the use of output Unit? 6. Write the different characteristics of the Computer. 7. Explain the use of each of the three components of the CPU. 8. What do you mean by storage unit? 9. Draw a block diagram of a computer showing its various components. 10. Write the differences between two types of memory. 11. What is the difference between hardware and software? 12. Name the two types of printers. 13. Give two examples each of input and output devices. 14. Arnav uses the given computer system for writing his reports.

Write the names of all the components shown and specify its use i.e. whether used for input/output/processing.

15. Which of the following devices can be categorized as a Secondary Storage Device? a) Keyboard b) Hard disk c) Pen drive d) CD ROM e) Mouse 16. Identify the given devices and write a line on each. a)

b)

c)

d)