Computer is a device that transforms data into meaningful information. It processes the input according to the set of instructions provided to it by the user and gives the desired output quickly. A Computer can perform the following set of functions:

• Accept data
• Store data
• Process data as desired
• Retrieve the stored data as and when required
• Print the result in desired format.

Data and Information:

Data: It is the term used for raw facts and figures fed into the computer and along with the set of instructions which enables the computer to convert this raw data into the refined and useful information.

Information: Data represented in useful and meaningful form is information.

Classification of Computers:
Computers can be classified based on the technology being used and the way they are designed to perform the various tasks. Computers can be categorized into Digital, Analog and Hybrid based on their design and working:

• Digital Computers : These are the modern computers which are capable of processing information in discrete form. In digital technology data which can be in the form of letters, symbols or numbers is represented in binary form i.e. 0s and 1s. The digital computers are used in industrial, business and scientific applications. They are quite suitable for large volume data processing.
• Analog Computers : These computers are used to process data generated by ongoing physical processes. A thermometer is an example of an analog computer since it measures the change in mercury level continuously. Analog computers are well suited to simulating systems. A simulator helps to conduct experiments repeatedly in real time environment. Some of the common examples are simulations in aircrafts, nuclear power plants, hydraulic and electronic networks.
• Hybrid Computers : These use both analog and digital technology. It has the speed of analog computer and the accuracy of a digital computer. It may accept digital or analog signals but an extensive conversion of data from digital to analog and analog to digital has to be done. Hybrid Computers are used as a cost effective means for complex simulations.

Classification of Digital Computers

Peripheral Devices

These devices are used for performing the specific functions and are connected to the computer externally. These peripheral devices enable the computer to operate according to the user requirements by feeding data in and out of the computer. Peripheral devices are as follows:

INPUT DEVICES : These devices accept data and instructions from the user. These include:
• Keyboard
• Mouse
• Light Pen
• Optical/magnetic Scanner
• Touch Screen
• Microphone for voice as input
• Track Ball

OUTPUT DEVICES :These devices return processed data that is information, back to the user. Some of the commonly used output devices are:

• Monitor (Visual Display Unit)
• Printers
• Plotter
• Speakers

Difference between RAM and Hard-disk

CPU process the data, and to process that data we need fast speed memory which is known as RAM.

Types of Software

1. System Software : These are those software,without which our PC,laptop won’t run, i.e it is must for a device to be operating.
   For Example: Linux,Unix,Windows,etc.
2. Application Software : These are those software,without which our PC,laptop can run, i.e these software are not necessary for a device to be operating.
   For Example: Facebook,What’s App,Games.

NOTE: In Earlier times i.e before 1970s,for making both these software we have to learn different languages.
For Example, Assembly language was used for System Software whereas Pascal,Cubel,etc. were used for making Application Software.

Difference between Hacker and Cracker

1. Hacker : They will just warn you something about malicious activity going around in your computer.It will not steal your information.
2. Cracker : They will try to steal your Information without informing you.