Explanation : 263 in binary form is 100000111. If one tries to print an integer as a character, only the last 8 bits will be considered - the rest chopped off. So, in this case, the ASCII value of 00000111 will be printed, Look in the ASCII table. It is ringing a bell!
Explanation : Let ab be 0 x MN. N&f should yield 7 i.e. N & 1111 should produce 0111. So, N should be 0111, i.e., 7. Similarly, M can be found to be 2. So, ab is 0 x 27.