What Is a Computer?

A computer is an electronic device capable of performing computations and making logical decisions at speeds millions, billions and even trillions of times faster than human being. For example, many of today's personal computers can perform a billion additions per second. A person operating a desk calculator could spend an entire lifetime performing calculations and still not complete as many calculations as even today's more modest personal computers can perform in one second. (Points to ponder: How would you know whether the person added the numbers correctly? How would you know whether the computer added the numbers correctly?) The most powerful computers are called supercomputers; some of these are already performing trillions of additions per second!

Computers process data under the control of sets of instructions called computer programs. These programs guide computers through orderly sets of actions that are specified by people known as computer programmers.

A computer consists of various devices referred to as hardware (e.g., the keyboard, screen, mouse, hard drive, memory, DVDs and processing units). The programs that run on a computer are referred to as software (e.g., word processing programs, e-mail and games). Hardware costs have been declining dramatically in recent years, to the point that personal computers have become a commodity. Historically, however, software development costs have risen steadily as programmers develop ever more powerful and complex applications without being able to significantly improve the software development process. In this book, you will learn object-oriented programminga technology that is dramatically reducing software development costs.