FORM is a symbolic manipulation program that has been designed for large scale formula manipulation. The formulae that can be handled by FORM are in principle only limited in size by the available disk space. In addition FORM is optimized for speed, enabling it to deal with these giant formulae in relatively little time. FORM runs as a batch program. One of the features of FORM is the management of really large formulae in a very efficient way. This is version 1 which is free; an improved version 2 is a commercial package.

(modified from the documentation)