Office/business application: Computer has become very important in offices and business world including bank, aviation, industry and communication organizations. Before now, there were lots of paper works in offices but today, the computer has reduced this as lots of information are stored directly into it. Examples of various business application are Payroll system: used to prepare staff salaries. Invoice control: given to a customer after a purchase has been made. Stock control: used in supermarket and departmental stores to keep a record of purchases made by customers and to know the current stock of goods in the store. Bank transaction such as deposit, withdrawal, funds transfer and customer information unit are all done in the bank.