CUPL is a second-generation language and processor designed specifically for introductory instruction in computer programming. It combines a severely simple syntax (based loosely on PL/I) and very extensive tutorial and diagnostic assistance by the processor. The processor is core-resident and compiles very rapidly. The result is an effective instructional system that can be used for large numbers of students with modest demands on computer capacity. Technically CUPL is interesting for the error-correctinng capability of the compiler and the provision of direct operations for matrix algebra.