A computer is a machine that can perform calculations using a set of instructions. Computers have input devices like keyboards and mice to enter information, and output devices like monitors, printers, and projectors to present information. Data storage devices like CDs, DVDs, and USB drives are used to transfer files between computers. The most important software is the operating system, which controls how hardware and other programs share resources. Common software includes word processors, spreadsheets, web browsers, and email programs, while specialized software exists for tasks like finance, drafting, and tutorials.