Two-bit signed data type:
Notice that when operands have opposite signs, their sum will never overflow:
1 + -2 = -1 1 + -1 = 0
Therefore, overflow can only occur when the operands have the same sign:
1 + 1 = 2 -2 + -2 = -4 -2 + -1 = -3
None of the results { 2, -4, -3 } can fit into the two-bit signed data type.