Abstract from the original ORTEP report
(Johnson, Carroll K., 1965. "OR TEP: A FORTRAN Thermal-Ellipsoid Plot Program for Crystal Structure Illustrations". ONRL Report #3794. Oak Ridge, Ten., Oak Ridge National Laboratory)
This report describes a computer program for drawing crystal structure illustrations witha mechanical plotter. Ball-and-Stick type illustrations of quality suitable for publications are produced with either spheres or thermal-motion probability ellipsoids on the atomic sites. The program can produce stereoscopic paris of illustrations which aid in the visualization of complex packing arrangements of atoms and thermal motion patterns. Interatomic distances, bond angles, and principal axes of thermal motion are also calculated to aid the structural study.
The FORTRAN coding utilizes the comparable features of IBM 709/7090 FORTRAN II and CDC 1604/1604A FORTRAN 63 so that the program can be executed on a number of different machines which hav 32K word memories. The machine-oriented plotting subroutines are standrad library type-type routines with slight modifications. Both CalComp and Benson Lehner off-line magnetic-tape plotting systems have been succesfully used.