Turbo Pascal 3 is probably the most wonderful compiler of all time: A complete Pascal compiler that fit into 39k and cost $40. Extensions for modular compilation, enhanced file handling, and PC graphics. It was the first compiler to allow a large number of people to write software in a high-level structured programming language (that is, code that other people could decipher).
In the early 1990's, Borland put a RAD front-end on Turbo Pascal, threw in their database engine, and named the combination Delphi.
Delphi was so successful it saved the company, which had been rocked by Microsoft's purchase of Fox Software after Borland had purchased Ashton-Tate.