Although you can enter AutoLISP code in the Visual LISP Console window or at the AutoCAD Command prompt, testing and debugging a series of instructions are considerably easier when you save AutoLISP code in a file rather than re-entering it each time you make a refinement. AutoLISP source code is usually stored in ASCII text files with an .lsp extension. However, you can load AutoLISP code from any ASCII text file.
To create a new source file in VLISP, click New File from the VLISP File menu bar.
To edit existing AutoLISP source code in VLISP, click Open File from the VLISP File menu bar, and use the Open File dialog box to select your file. VLISP loads this file into its text editor and displays the contents in a new editor window.