XTAL: new concepts in program system design

Program systems are used extensively for crystallographic computing. Most existing systems have problems with language incompatibility, computational inefficiency and poor adaptability. This is because many desirable features demand opposing strategies in system design. Systems development is also complicated by the increasing number of computer types and sizes capable of doing crystallographic calculations. This, coupled with the widening aspirations of crystallographers, is making the task of developing an efficient and comprehensive program system increasingly difficult, particularly with conventional Fortran programming methods. The XTAL system is being developed with a different approach to these problems. The distribution of XTAL source code is in the RATMAC preprocessor language, the use of efficient machine-specific code is encouraged, and a much more flexible directory-type file structure is used for archive data files.