The header file <stdlib.h> defines a number of types, macros, and functions of general utility.
div_t, ldiv_t, lldiv_t
RAND_MAX
atoi, atol, atoll, itoa, ltoa, lltoa, strtol, strtoll, strtoul, strtoull, ultoa, ulltoa, utoa
div, ldiv, lldiv
rand, srand