QBasic
Qbasic has been around for... for... Ever! Ok. Since 1991. It is based
off QuickBasic (a basic complier) but without the complier and linker. It only
functions as a interpreter so it can't make stand alones (EXEs). It has its' own built in IDE
and inline error handling. This will only catch simple typos. For a programing language it is
a bit dated, but it is free, easy to understand, and will run on anything! From MS-Dos 3.2 to
Windows Vista and Linux. I would recommend running Qbasic through DosBox for XP or Vista.