Answer 1

The output is 'b'.
This is equivalent with printf("%c",('c'-1));

printf("%x",('c'*-1)); - this will give the representation in hex for ('c'*-1), this can be convert in binary and '~' is used to complement that binary, wich means 0 will be 1 and 1 will be 0. After that you can convert that binary to char with the Ascii table, and you will see that is 'b'