cstdlib

1. atof() --> converts string to double
2. bsearch() --> performs binary search on a sorten array
3. calloc() --> allocates a block of memory and initializes it to 0
4. abs() --> returns the absolute value of an integer
5. div() --> quotient and remainder of an integer
6. free() --> de-allocates a block of memory
7. getenv() --> returns pointer to environment variable passed
8. labs() --> absolute value of a long or long int
9. malloc() --> allocates a block of uninitialized memory
10. qsort() --> sorts an array using quick-sort algorithm
11. realloc() --> reallocates a block of previously allocated memory
12. srand() --> seeds a pseudo random number for rand()
13. strtol() --> converts a string to an integer
14. strtoull() --> converts string to unsigned long long int

unistd.h (standard symbolic constants and types)

sys/types.h (data types)

Collection of typedef symbols and structures Find details here and here