The word "computer" comes from the word "compute", which means, to calculate.Hence,people usually consider a computer to be a calculating device that can perform arithmetic operations at high speed. Although the original objective of inventing a computer was to create a fast calculating device, we now define a computer as a device that operates upon data because more than 80%of work done by today's computers is data processing. Data can be anything like bio-data of applicants when computer is used for short listing candidates for recruiting; marks obtained by students in various subjects when used for preparing results;details (name,age,sex,etc.) of passengers when used for making airline or railway reservations; or number of different parameters when used for solving scientific research problems, etc. Notice from the examples that data can be either numerical, non-numerical, or a mixture of both.
A computer is often referred to as a data processor because it can store, process and retrieve data whenever desired. The name data data processor is more inclusive because modern computers not only compute in the usual sense but also perform other functions which data that flows to and form them. For example, data processor may gather data from various incoming sources, merge (process of mixing or putting together) them all, sort (process of arranging in some sequence-ascending or descending) them in the desired order, and finally print them in desired format. Notice that none of these operations involves arithmetic copulations in the usual sense but a computer is the most suitable device for performing them.
The activity of processing data using a computer is called data processing. Data processing consists of three sub-activities: capturing input data, manipulating the data, and managing output results.
As used in data processing, information is data arranged in an order and form that is useful to people receiving it. Hence, data is raw material used as input to data processing and information is processed data obtained as output of data processing.