ABSTRACT
The use of S language requires some basic familiarity with interactive computing: how to log into the UNIX system, what keys to use on the terminal to delete characters and lines and to send interrupts, etc. A good way to start thinking about S is to compare it to a very powerful calculator. Expressions are made up by combining object names and constants with operators and functions. Operators include the usual arithmetic operations, comparisons, and a few special operators. Generally, names can contain letters, digits, and periods, and must start with a letter. Although it is a good idea to use meaningful names for objects, a name need bear no relation to the contents of the object and names can be reused whenever desired. S expressions can have character string values as well as numerical or logical ones. Data can be extracted from an object by using an expression in square brackets following the name of the object.
