整型
signed char 1 -2^7 ~ 2^7-1 -128～+127
short int 2 -2^14 ~ 2^14-1 -32768～+32767
int 4 -2^31 ~ 2^31-1 -2147483648～+2147483647
unsigned int 4 0 ~ 2^32-1 0 ~ 4294967295
long int 4 -2^31 ~ 2^31-1 -2147483648～+2141483647 （同int）
unsigned long 4 0 ~ 2^32-1 0～4294967295
long long int 8 -2^63 ~ 2^63-1 -9223372036854775808～+9223372036854775807
unsigned long long 8 0 ~ 2^64-1 18446744073709551615
