chechout the wiki all of it is there!
[done] - 0: file of chars, strings, presentage.
[done] - 1: file of dicimales, integers.
[done] - 2: file of binary.
[working on] - 3: file unsigned, octal, hex.
[done] - 4: file of Use a local buffer of 1024 chars in order to call write as little as possible.
[done] - 5: file that prints the string s.
[x] - 6: file of specifier p.
[x] - 7: file of flag characters. +, space and #.
[x] - 8: file of length modifires.
[x] - 9: file of field width.
[x] - 10: file of precision.
[x] - 11: file of the 0 flag character.
[x] - 12: file of the - flag character.
[x] - 13: file of the reversed string.
[x] - 14: file of the rot13'ed string.
[x] - 15: all the above options work well together.