Software

A computer that is dedicated to running a program that controls another device is an embedded system. An embedded system is usually embedded inside the device it controls. Usually they run just one program that is permanently kept in a special kind of main memory called ROM (for Read Only Memory). More processor chips are sold per year for embedded systems than for all other purposes.

Software is the programs and data that a computer uses. Software is kept on some hardware device such as a hard disk or floppy disk, but it itself is intangible. Say that you have a floppy disk with a program saved on it. Now say that you erase the program from the disk. The atoms and molecules of the disk are the same ones as before, but now the program is "gone." The intangible software has been removed without removing anything tangible.

Software consists of both programs and data. Programs are lists of instructions for the processor. Data can be any information that a program needs: character data, numerical data, image data, audio data, and countless other types. The distinction between programs and data is not as clear-cut as you might think, however.

Fundamental Idea: Both programs and data are saved in computer memory in the same way. The electronics of computer memory (both main memory and secondary memory) make no distinction between programs and data.

The insight that both programs and data can be saved using the same electronic methods is one of the most important ideas in computer science. Computer systems can use their memory for whatever needs arise.