coordination of activities and the sharing of the resources of the computer. The operating system communicates between the applications that are run on the machine and the machine’s hardware components. • Prompt: This visual cue tells the user to input something. • Script and application: The terms “script,” “application,” and “program” are used somewhat interchangeably in this book, though there are some subtle differences in meaning: • Script: This short but complete piece of code is intended to be run using an interpreter. A script will exist as a text file that you can read. • Application: This refers to any applied use of a programming language. It usually means a complete, packaged-up, and usable piece of software. It is the preferred term among Linux/Unix users. • Program: This refers to the sequence of instructions involved in a script or application; it is also used as a general term to describe an executable computer file. • Software development cycle: In this structured approach to developing software, each stage can be fed back into previous stages. See Chapter 2. • Version number: This number corresponds to a new development in a piece of software. These numbers may refer to major or minor changes and are generally assigned in increasing order. The method used for assigning these numbers is referred to as a versioning system.