Since 1935, a great number of crystal structures have been solved by the Patterson technique and recently the symbolic addition procedure is becoming a major crystallographic tool, especially for organic compounds with no heavy atom. To solve the crystal structure without any human intervention the auther has constructed a large program system which has been made up of several crystallographic computer programs. It is intended for use by organic chemists rather than professional crystallographers. The program system, written in FORTRAN-63 for a CDC 6600 computer with a 131 K core strage and 60-bit word-length, may be run either separately or in combination. The input data are the highest E reflexions (|E|>1. 5, E being normalized structure factor), cell constants, symmetry card, atomic scattering factor tables, and number and types of atoms in the unit cell. The outputs are a projection diagram of the molecules in a unit cell, atomic co-ordinates and bond distances. The program system has been successful over a considerable range of space groups.
