Computers have two major components: the hardware and the software. Hardware consists of all the physical devices needed to actually build and operate a computer. Examples of computer hardware are the central processing unit (CPU), hard drive, memory, modems, and external devices such as the keyboard, monitor, printers, scanners, and other devices that can be physically touched. Software is an integral part of a computer and consists of the various computer programs that allow the user to interact with it and specify the tasks the computer performs. Without software, a computer is merely a collection of circuits and metal in a box unable to perform even the most basic functions.