A computer is an electronic machine that performs calculations based on a set of instructions. The first computers were huge, room-sized machines that took teams of people to build, manage and maintain. The computer systems of today are exponentially faster and only a fraction of the size of those original computers.

A computer system consists of hardware and software components. Hardware is the physical equipment. It includes the case, storage drives, keyboards, monitors, cables, speakers, and printers. Software includes the operating system and programs. The operating system instructs computer operations. These operations can include identifying, accessing, and processing information. Programs or applications perform different functions. Programs vary widely depending on the type of information that is accessed or generated. For example, instructions for balancing a checkbook are different from instructions for simulating a virtual reality world on the Internet.