在标准c头文件中包含了对最大最小值的定义

limits.h(vs2005)

#define CHAR_BIT      8         /* number of bits in a char */ #define SCHAR_MIN   (-128)      /* minimum signed char value */ #define SCHAR_MAX     127       /* maximum signed char value */ #define UCHAR_MAX     0xff      /* maximum unsigned char value */

#ifndef _CHAR_UNSIGNED #define CHAR_MIN    SCHAR_MIN   /* mimimum char value */ #define CHAR_MAX    SCHAR_MAX   /* maximum char value */ #else #define CHAR_MIN      0 #define CHAR_MAX    UCHAR_MAX #endif  /* _CHAR_UNSIGNED */

#define MB_LEN_MAX    5             /* max. # bytes in multibyte char */ #define SHRT_MIN    (-32768)        /* minimum (signed) short value */ #define SHRT_MAX      32767         /* maximum (signed) short value */ #define USHRT_MAX     0xffff        /* maximum unsigned short value */ #define INT_MIN     (-2147483647 - 1) /* minimum (signed) int value */ #define INT_MAX       2147483647    /* maximum (signed) int value */ #define UINT_MAX      0xffffffff    /* maximum unsigned int value */ #define LONG_MIN    (-2147483647L - 1) /* minimum (signed) long value */ #define LONG_MAX      2147483647L   /* maximum (signed) long value */ #define ULONG_MAX     0xffffffffUL  /* maximum unsigned long value */ #define LLONG_MAX     9223372036854775807i64       /* maximum signed long long int value */ #define LLONG_MIN   (-9223372036854775807i64 - 1)  /* minimum signed long long int value */ #define ULLONG_MAX    0xffffffffffffffffui64       /* maximum unsigned long long int value */

计算的方法

有符号

max=((unsigned type)(~0))>>1;

min= ~max；

无符号

max = (unsigned type)(~0);

min = 0;