here b should show the value '2147483648' but the maximum positive number is '2147483647'. Actually these values lie in circular form so the desired result is 2147483648 i.e. '2147483647+1' so when we add 1 to 2147483647, the value becomes -2147483648.
There is no concept of overflow error/exception in integer arithmetic. When you negate the largest negative number, you get a positive number which is out of range of integer. So it wraps to the smallest no which is again the integer minimum value.