AutoLISP is a programming language that allows AutoCAD users to create programs to customize AutoCAD. It is one of the simplest programming languages to learn and use. AutoLISP is useful for 2 main reasons. AutoLISP can automate repetitive procedures and it can also be used to create completely new commands, from simple to complex calculations and for creating completely finished drawings. Because AutoLISP is an interpreted language rather than a compiled language, a program can be written, saved in a plain ASCII text file, and then loaded into memory inside AutoCAD. Once a program has been loaded, it can be run from the command prompt, a pull down menu or tool bar. AutoCAD has a built in editor called Visual LISP (VLIDE command) interactive development environment program.