获取C语言中的最大值(正无穷)与最小值(负无穷)的一些方法与技巧

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#include <stdio.h>
int main(){
printf("INT_MAX = %dn",unsigned(-1)>>1);
//编译器默认-1为int型，所以在转换为unsigned型后并右移一位中，最高位也要随之移动。
printf("-INT_MAX = %dn",-(unsigned(-1)>>1)-1); //由于计算机采用的补码方式存储，所以对于int型的最小值则为-2^31，也即 -INT_MAX-1。
printf("UNSIGNED_INT_MAX = %un",unsigned(-1)); //由于-1的补码的二进制位全为1。所以unsigned(-1)的编码为全1状态的无符号的值。也即无符号的最大值。
return 0;
}

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/*
C语言中的整数类型
int 是 C 语言的基本整数类型，可以满足我们处理一般数据的需求。
C 语言还提供了四个可以修饰 int 的关键字：short、long、signed，以及 unsigned。
利用这四个关键字，C 语言标准定义了以下整数类型：
1) short int（可简写为 short），和 int 一样，也是有符号整数
2) long int（简写：long），有符号整数
3) long long int（简写：long long），<span style="color:#ff0000;">C99标准</span>添加的类型，有符号整数
4) unsigned int（简写：unsigned），无符号整数，不能表示负数
5) unsigned long int（简写：unsigned long），无符号整数，不能表示负数
6) unsigned short int（简写：unsigned short），无符号整数，不能表示负数
7) unsigned long long int（简写：unsigned long long），C99添加的类型，无符号整数
8) <span style="color:#ff0000;">所有没有标明 unsigned 的整数类型默认都是有符号整数。</span>
在这些整数类型前面加上 signed 可以使读者更清楚地知道
这些是有符号整数，尽管有没有 signed 都表示有符号整数。
例如：signed int 等同于 int 。
注意：C语言只规定short <= int <=long int。<span style="color:#ff0000;">具体还得看具体的编译器，long int型并不能肯定就是64位的，很多时候long int和int表示的范围是一致的。</span>
一般我们把 short 称为短整型，把 long 称为长整型，把 long long 称为超长整型，把 int 称为整型。unsigned 打头的那些整数类型统称为无符号整型。
例如：我们称 unsigned short 为无符号短整型。以此类推。
*/

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#include <stdio.h>
#include <limits.h>
int main(){
printf("INT_MAX = %d(2*10^10)n",INT_MAX);
//括号内为大约的级数
printf("INT_MIN = %d(-2*10^10)n",INT_MIN);
printf("UINT_MAX = %u(4*10^10)n",UINT_MAX);
printf("LONG_LONG_MAX = %lld(9*10^19)n",LLONG_MAX);
printf("LONG_LONG_MIN = %lld(-9*10^19)n",LLONG_MIN);
printf("UNSIGNED_LONG_LONG_MAX = %<span style="color:#ff0000;">llu</span>(1*10^20)n",ULONG_LONG_MAX);
return 0;
}

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/**
* @file limits.h
* Copyright 2012, 2013 MinGW.org project
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
#ifndef _LIMITS_H
#define _LIMITS_H
#pragma GCC system_header
#include <_mingw.h>
/*
* Functions for manipulating paths and directories (included from io.h)
* plus functions for setting the current drive.
*
* Defines constants for the sizes of integral types.
*
* NOTE: GCC should supply a version of this header and it should be safe to
*
use that version instead of this one (maybe safer).
*/
/*
* File system limits
*
* TODO: NAME_MAX and OPEN_MAX are file system limits or not? Are they the
*
same as FILENAME_MAX and FOPEN_MAX from stdio.h?
* NOTE: PATH_MAX is the POSIX equivalent for Microsoft's MAX_PATH; the two
*
are semantically identical, with a limit of 259 characters for the
*
path name, plus one for a terminating NUL, for a total of 260.
*/
# define PATH_MAX	260
/*
* Characteristics of the char data type.
*
* TODO: Is MB_LEN_MAX correct?
*/
#define CHAR_BIT	8
#define MB_LEN_MAX	2
#define SCHAR_MIN	(-128)
#define SCHAR_MAX	127
#define UCHAR_MAX	255
#ifndef _CHAR_UNSIGNED
#define CHAR_MIN	SCHAR_MIN
#define CHAR_MAX	SCHAR_MAX
#else
#define CHAR_MIN	0
#define CHAR_MAX	UCHAR_MAX
#endif
/*
* Maximum and minimum values for ints.
*/
#define INT_MAX
2147483647
#define INT_MIN
(-INT_MAX-1)
#define UINT_MAX	0xffffffff
/*
* Maximum and minimum values for shorts.
*/
#define SHRT_MAX	32767
#define SHRT_MIN	(-SHRT_MAX-1)
#define USHRT_MAX	0xffff
/*
* Maximum and minimum values for longs and unsigned longs.
*/
#define LONG_MAX	2147483647L
#define LONG_MIN	(-LONG_MAX-1)
#define ULONG_MAX	0xffffffffUL
#define SSIZE_MAX LONG_MAX
#define LLONG_MAX 9223372036854775807LL
#define LLONG_MIN (-LLONG_MAX - 1)
#define ULLONG_MAX (2ULL * LLONG_MAX + 1)
#define LONG_LONG_MAX	9223372036854775807LL
#define LONG_LONG_MIN	(-LONG_LONG_MAX-1)
#define ULONG_LONG_MAX	(2ULL * LONG_LONG_MAX + 1)
/* MSVC compatibility */
#define _I64_MIN LONG_LONG_MIN
#define _I64_MAX LONG_LONG_MAX
#define _UI64_MAX ULONG_LONG_MAX
#endif /* not _LIMITS_H */<strong>
</strong>