What data is

People make decisions from data: choosing a college from its placement records, faculty and fees; governments planning from the census; coaches studying opponents' past games; banks keeping customers' accounts and transactions.

What data is. Data is a collection of characters, numbers and other symbols that represent values of some situations or variables. 'Data' is plural; the singular is 'datum'. Computers store data electronically, which makes processing faster than doing it by hand, and the ICT revolution (computers, mobiles, the Internet) produces huge volumes of it.

• Examples: a person's name, age, gender and contact details; transactions from banking, ticketing and shopping; images, audio and video; documents and web pages; online posts, comments and messages; signals from sensors; satellite data (weather, communication, earth observation).

Raw data alone does not give a decision. A college may hold placement data of about 2,000 students over three years, but no one can judge it by looking at the raw list. It must be gathered, processed and analysed, and the results summarised (as in a placement brochure with charts).

Why data matters:

• When you withdraw money from an ATM, the bank must update your account balance.
• Weather offices watch satellite data for cyclones and heavy rain; weather alerts come from analysing it.
• Businesses track market behaviour and customer feedback. Dynamic pricing (airlines, railways, cab apps) sets prices from demand and supply; restaurants plan 'happy hours' discounts from sales at different times.
• Electronic voting machines record votes so results can be declared quickly; scientists record experiment data; drug companies record trial data; libraries track books and members; search engines analyse huge amounts of web data.

Example (new): a school canteen that records which snacks sell each day may find that samosas sell out by 11 a.m. on Mondays; using that data, it can cook more on Mondays and waste less on other days.