VMS Help CC, Run-time functions, ecvt  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  Converts its value argument to a null-terminated string of ASCII
  digits and returns the address of the string.  The string is stored
  in a memory location created by the function.

  Syntax:

       #include <stdlib.h>

       char *ecvt(double value, int ndigit, int *decpt, int *sign);