limits.h

limits.h專門用於檢測整型數據數據類型的表達值範圍。

基本介紹

• 中文名：極限頭檔案
• 外文名：<limits.h>或<climits>
• 用途：檢測整型數據數據類型表達值範圍
• 判斷類型：可以容納的最大值或最小值
• 性質：檢測表達值

基本釋義

limits.h包含內容（包括注釋）

/*

* limits.h

* This file has no copyright assigned and is placed in the Public Domain.

* This file is a part of the mingw-runtime package.

* No warranty is given; refer to the file DISCLAIMER within the package.

*

* 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).

*

*/

#ifndef _LIMITS_H_

#define _LIMITS_H_

/* All the headers include this file. */

#include <_mingw.h>

/*

* 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: Apparently the actual size of PATH_MAX is 260, but a space is

* required for the NUL. TODO: Test?

*/

#define PATH_MAX (259)

/*

* 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

/* TODO: Is this safe? I think it might just be testing the preprocessor,

* not the compiler itself... */

#if ('\x80' < 0)

#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.

*

* TODO: This is not correct for Alphas, which have 64 bit longs.

*/

#define LONG_MAX 2147483647L

#define LONG_MIN (-LONG_MAX-1)

#define ULONG_MAX 0xffffffffUL

/*

* The GNU C compiler also allows 'long long int'

*/

#if !defined(__STRICT_ANSI__) && defined(__GNUC__)

#define LONG_LONG_MAX 9223370L

#define LONG_LONG_MIN (-LONG_LONG_MAX-1)

#define ULONG_LONG_MAX (2ULL * LONG_LONG_MAX + 1)

/* ISO C9x macro names */

#define LLONG_MAX LONG_LONG_MAX

#define LLONG_MIN LONG_LONG_MIN

#define ULLONG_MAX ULONG_LONG_MAX

/* MSVC compatibility */

#define _I64_MIN LONG_LONG_MIN

#define _I64_MAX LONG_LONG_MAX

#define _UI64_MAX ULONG_LONG_MAX

#endif /* Not Strict ANSI and GNU C compiler */

#endif /* not _LIMITS_H_ */

補充內容

要判斷某種特定類型可以容納的最大值或最小值，一種簡便的方法是使用ANSI標準頭檔案limits.h中的預定義值。該檔案包含一些很有用的常量，它們定義了各種類型所能容納的值，下表列出了這些常量：

常 量 描 述

CHAR_BIT char的二進制位數(bit)

CHAR_MAX char的有符號整數最大值

CHAR_MIN char的有符號整數最小值

MB_LEN_MAX 多位元組字元的最大位元組(byte)數

INT_MAX int的有符號最大值

INT_MIN int的有符號最小值

LONG_MAX long的十進制最大值

LONG_MIN long的十進制最小值

SCHAR_MAX signedchar的十進制整數最大值

SCHAR_MIN signedchar的十進制整數最小值

SHRT_MIN short的十進制最小值

SHRT_MAX short的十進制最大值

UCHAR_MAX unsignedchar的十進制整數最大值

UINT_MAX unsignedint的十進制最大值

ULONG_MAX unsignedlongint的十進制最大值

USHRT_MAX unsignedshortint的十進制最大值

對於整數類型，在使用2的補碼運算的機器(你將使用的機器幾乎都屬此類)上，一個有符號類型可以容納的數字範圍為[- 2^(位數-1) ]到[+ 2^(位數 -1)-1]，一個無符號類型可以容納的數字範圍為0到(+ 2^位數 )。例如，一個16位有符號整數可以容納的數字範圍為-2^15(即-32768)到(+2^15-1)(即+32767)。而16為無符號整數可容納的最大值為(2^位數-1)或表示為彙編形式0xffff。