例如:
short int i = 1 ; 与 short i = 1 ; 等价。
unsigned short int i = 2 ; 与 unsigned short i = 2 ; 等价。
unsigned int i = 3 ; 与 unsigned i = 3 ; 等价。
long int i = 4 ; 与 long i = 4 ; 等价。
unsigned long int i = 5 ; 与 unsigned long i = 5 ; 等价。