int

　　The int data type is used for variaables that will store integers.

　　Intergers always take up 4bytes of memory(32bits).This means the range of values they can store is necessarily limited to 32 bits worth of information.

unsigned int

　　Unsigned is a qualifier that can be applied to certain types (including int),which effectively doubles the positive range of variable of that type, at the cost of disallowing any negative values.