The IMSL Libraries consist of two separate, but coordinated Libraries that allow easy user access. These Libraries are organized as follows:

Most of the routines are available in both single and double precision versions. Many routines are also available for complex and complex‑double precision arithmetic. The same user interface is found on the many hardware versions that span the range from personal computer to supercomputer. Note that some IMSL routines are not distributed for FORTRAN compiler environments that do not support double precision complex data. The specific names of the IMSL routines that return or accept the type double complex begin with the letter “Z” and, occasionally, “DC.”