0x07-pointers_arrays_strings

Tasks for this project:

0. Write a function that fills memory with a constant byte
1. Write a function that copies memory area
2. Write a function that locates a character in a string
3. Write a function that gets the length of a prefix substring
4. Write a function that searches a string for any of a set of bytes
5. Write a function that locates a substring
6. Write a function that prints the chessboard
7. Write a function that prints the sum of the two diagonals of a square matrix of integers
8. Write a function that sets the value of a pointer to a char