被无穷大和无穷小难道

C语言中，如何表示无穷大，无穷小。

无穷大(小)是数学概念，编程中不会出现无穷的东东，所以完全可以用能表示的最大的数，或最大的数来代替。

在头文件limits.h中有各种类型的数的最大值，最小值的符号常量定义，便于直接使用，例如变量的初始化。

例如：

　　INT_MAX 是int的十进制最大值

　　INT_MIN 是int的十进制最小值

　　LONG_MAX是 long的十进制最大值

　　LONG_MIN 是long的十进制最小值

　　UCHAR_MAX是 unsignedchar的十进制整数最大值

　　UINT_MAX 是unsignedint的十进制最大值

/***
*limits.h - implementation dependent values
*
*       Copyright (c) Microsoft Corporation.  All rights reserved.
*
*Purpose:
*       Contains defines for a number of implementation dependent values
*       which are commonly used in C programs.
*       [ANSI]
*
*       [Public]
*
****/
#if     _MSC_VER > 1000
#pragma once
#endif
#include <crtdefs.h>
#ifndef _INC_LIMITS
#define _INC_LIMITS

#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 */
#define _I8_MIN     (-127i8 - 1)    /* minimum signed 8 bit value */
#define _I8_MAX       127i8         /* maximum signed 8 bit value */
#define _UI8_MAX      0xffui8       /* maximum unsigned 8 bit value */
#define _I16_MIN    (-32767i16 - 1) /* minimum signed 16 bit value */
#define _I16_MAX      32767i16      /* maximum signed 16 bit value */
#define _UI16_MAX     0xffffui16    /* maximum unsigned 16 bit value */
#define _I32_MIN    (-2147483647i32 - 1) /* minimum signed 32 bit value */
#define _I32_MAX      2147483647i32 /* maximum signed 32 bit value */
#define _UI32_MAX     0xffffffffui32 /* maximum unsigned 32 bit value */
/* minimum signed 64 bit value */
#define _I64_MIN    (-9223372036854775807i64 - 1)
/* maximum signed 64 bit value */
#define _I64_MAX      9223372036854775807i64
/* maximum unsigned 64 bit value */
#define _UI64_MAX     0xffffffffffffffffui64
#if     _INTEGRAL_MAX_BITS >= 128
/* minimum signed 128 bit value */
#define _I128_MIN   (-170141183460469231731687303715884105727i128 - 1)
/* maximum signed 128 bit value */
#define _I128_MAX     170141183460469231731687303715884105727i128
/* maximum unsigned 128 bit value */
#define _UI128_MAX    0xffffffffffffffffffffffffffffffffui128
#endif
#ifndef SIZE_MAX
#ifdef _WIN64 
#define SIZE_MAX _UI64_MAX
#else
#define SIZE_MAX UINT_MAX
#endif
#endif
#if __STDC_WANT_SECURE_LIB__
/* While waiting to the C standard committee to finalize the decision on RSIZE_MAX and rsize_t,
 * we define RSIZE_MAX as SIZE_MAX
 */
#ifndef RSIZE_MAX
#define RSIZE_MAX SIZE_MAX
#endif
#endif
#ifdef  _POSIX_
#define _POSIX_ARG_MAX      4096
#define _POSIX_CHILD_MAX    6
#define _POSIX_LINK_MAX     8
#define _POSIX_MAX_CANON    255
#define _POSIX_MAX_INPUT    255
#define _POSIX_NAME_MAX     14
#define _POSIX_NGROUPS_MAX  0
#define _POSIX_OPEN_MAX     16
#define _POSIX_PATH_MAX     255
#define _POSIX_PIPE_BUF     512
#define _POSIX_SSIZE_MAX    32767
#define _POSIX_STREAM_MAX   8
#define _POSIX_TZNAME_MAX   3
#define ARG_MAX             14500       /* 16k heap, minus overhead */
#define LINK_MAX            1024
#define MAX_CANON           _POSIX_MAX_CANON
#define MAX_INPUT           _POSIX_MAX_INPUT
#define NAME_MAX            255
#define NGROUPS_MAX         16
#define OPEN_MAX            32
#define PATH_MAX            512
#define PIPE_BUF            _POSIX_PIPE_BUF
#define SSIZE_MAX           _POSIX_SSIZE_MAX
#define STREAM_MAX          20
#define TZNAME_MAX          10
#endif  /* POSIX */
#endif  /* _INC_LIMITS */