ABSTRACT This package provides a Library of the elementary maths functions for the DECUS C system. The functions have the same names, arguments and functionality as their counterparts in UNIX so that porting applications programs from UNIX and UNIX compatible systems is facilitated. The functions provided are sqrt, log, log10, exp, pow, sin, cos, tan, cotan, asin, acos, atan, atan2, sinh, cosh, tanh, fabs, floor, ceil, frexp, ldexp and modf together with new versions of atof and $$dtoa. Most of the algorithms are from Cody and Waite "Software Manual for the Elementary Functions", Prentice-Hall, which have been designed to have a high level of accuracy throughout the entire range of their arguments. The test programs from that book are included also, as are a number of patches which fix bugs in the compiler module CC103 and the runtime modules DOPRNT, DOSCAN, FCLOSE and IOABUF.