A cookie is often used to identify a user. A cookie is a small file that the server embeds on the user's computer. Each time the same computer requests a page with a browser, it will send the cookie too. With PHP, you can both create and retrieve cookie values.A cookie is created with thesetcookie()function.

Computer is an electronic data processing device capable of taking an input data, processing them and displaying the processed result at a very high speed under the control of set of instructions. The four features of computer are :

• Speed
• Accuracy
• Versatility
• Diligence

Data is defined as the raw facts or symbols which are collected from various sources and need to be processed.

Information is defined as the desired or meaning full result obtained after processing the data.

The capabilities of computer are listed below :

• Computers operate at a very high speed, in fact with the speed of light.
• Computers operate nearly 100% accurately.
• Computers is capable of functioning automatically.
• Computer is a versatile device.
• Computer stores large volume of data and information.

Computer is called diligence machine because it can perform the task repeatedly without loosing its speed and accuracy for long time.

The circuitries of computers are designed on the basis of electrical signals and data travel them as the speed of current, therefore the computer is able to perform any task at the high speed.

The features of computer are listed below:
-Speed
-Accuracy
-Diligence
-Versatility
-Storage
-Automatic

The difference between GIGO and Bug are listed below:

A computer is called a diligent machine because of its capability of performing the tasks repeatedly for a long time without losing accuracy and speed.

A computer is called a versatile machine because of its capability of performing a variety of tasks.

The limitations of computers are listed below:
- Sinceit is a programmable electronic machine, it cannot work without the programs.
- It performs only those tasks which are instructed by the program.
- It cannot use its own logic and learn anything by performing the tasks.

The Abacus is the first calculating device developed by human beings which is made up of a wooden frame having two parts- upper deck and lower deck which contains 11 vertical rods with each rod consisting of movable beads.
Each rod contains two beads in the upper deck (also called Heaven) and five beads in the lower deck (also called Earth).

Napier's bones was the calculating device invented by John Napier and was based on the principle of logarithm which consisted of 11 sets of rectangular shaped bone rods carved with the logarithm values.

Charles Babbage is considered as the father of computer since the idea used in his analytic engine led to the development of the first electromechanical computer ‘Mark-I’.

A French mathematician, Blaise Pascal, invented the first mechanical calculator ‘Pascaline’ in 1642 AD.

Any four reasons for using computers in education sector are listed below:
- To increase the access to education.
- To improve the quality of teaching and learning.
- To improve knowledge sharing.
- To increase the efficiency and effectiveness in admission and classrooms.
- To provide online courses for those who are looking to obtain degrees without quitting their jobs.

Any four reasons for using computers in the health sector are listed below:
- To keep the records of patients and medical information.
- To diagnose the diseases of the patients.
- To perform surgical operations.
- To monitor the condition of patients continuously.
- To research the cause of diseases.
- To research new medicines.

Any reasons for using computers in business are listed below:
- To send/receive emails.
- To provide efficient services to the customers.
- To maintain an account of business.
- To promote the business via social media marketing, email campaigns, etc.
- To do business remotely from all over the globe.
- To store data in an organizedway which allows for easy access and use.
- To keep the data and information securely.
- To make a paperless environment.
- To do sales analysis and financial forecasting.
-...

A computer is a programmable and electronic device that can accept data and instructions as input, process them and produce desired results as output, also store if necessary.