1. prepare a function that reads a string of digits, possibly preceded by + or -, and converts this string to the integer value it represents. Be sure that your function checks that the string is well formed, that is, that it represents a valid integer. (Hint: use the functions provided in and ).
Also, prepare a driver programs to test the function.
2. prepare functions to implement the split, merge, and mergesort algorithms for files. Also, prepare driver programs to test the given functions.