On Reversible Subroutines and Computers that Run Backwards
A computer design is describe which permits
subroutines to be executed backward as well as 
forward, either with their instructions unchanged or
replaced with conjugate instructions.  It is shown 
that using this concept a number of new subroutine types
can be developed with rather unusual properties. 
 Since these properties are analogous to certain matrix
operations, a parallel nomenclature is suggested 
for their classification.
CACM September, 1965
Reily, E. D.
Federighi, F. D.
