数据类型 长度(字节) 值域 char 1 ASCII码字符 unsigned char 1 -128~127 signed char 1 0~255 unsigned int 4 0~4294967296 int/signed int 4 -2147483648- 2147483647 unsigned short/unsigned short int 2 0~ 65535 short/short int/signed short/signed short int 2 - 32768~ 32767 unsigned long/unsigned long int 8 0~1.8447e+019 long/long int/signed long/signed long int 8 -9.2234e+018~9.2234e+018 float 4 约精确到小数点后6位数 double 8 约精确到小数点后15位数