Turbo Pascal, aka Borland Pascal, is a cheap and powerful IDE for the MS-DOS environment. It uses Pascal and from version 5 onwards Object Pascal as its main programming language. The compiler component of Turbo Pascal was based on the Blue Label Pascal compiler originally produced for the NasSys cassette-based operating system of the Nascom microcomputer in 1981 by Anders Hejlsberg. This was first rewritten as the Compass Pascal compiler for the CP/M operating system and then as the Turbo Pascal compiler for the MS-DOS operating system and CP/M.