30.2.2 Use of C

C was first used in CONGEN for implementing the conformational search algorithm. This algorithm required complicated data structure processing and recursion, for which the language is eminently suitable. Later on, C was used for operating system interfaces because many of the operating system calls in C are portable. For example, the storage management Fortran library uses malloc in the C library to obtain additional storage from the operating system without a requirement for machine dependent code.

One limitation in the use of C is I/O. The Fortran and C I/O libraries are not compatible. Therefore, all I/O from C must be done using Fortran routines. See the source code for for_printf, for_scanf, etc. in cutil.c for routines which provide this functionality.