limits.h

整型的最大值和最小值

Content

整数值的最大值和最小值非常有用，或者简单地说，任何整数类型的极限在编程中都起着重要作用。无需记住这些值，可以使用不同的宏。**<climits>(limits.h)**定义整数类型的大小。[2]

• 此头定义了用于特定系统和编译器实现的基本整数类型的限制常量。

• 基本浮点类型的限制在 <cfloat> (<float.h>) 中定义。

• 宽度特定的整数类型和其他 typedef 类型的限制在 <cstdint> (<stdint.h>) 中定义。

name[1]	expresses	possible value*
CHAR_BIT	Number of bits in a char object (byte)	8 or greater*
SCHAR_MIN	Minimum value for an object of type signed char	-127 (-27+1) or less*
SCHAR_MAX	Maximum value for an object of type signed char	127 (27-1) or greater*
UCHAR_MAX	Maximum value for an object of type unsigned char	255 (28-1) or greater*
CHAR_MIN	Minimum value for an object of type char	either SCHAR_MIN or 0
CHAR_MAX	Maximum value for an object of type char	either SCHAR_MAX or UCHAR_MAX
MB_LEN_MAX	Maximum number of bytes in a multibyte character, for any locale	1 or greater*
SHRT_MIN	Minimum value for an object of type short int	-32767 (-215+1) or less*
SHRT_MAX	Maximum value for an object of type short int	32767 (215-1) or greater*
USHRT_MAX	Maximum value for an object of type unsigned short int	65535 (216-1) or greater*
INT_MIN	Minimum value for an object of type int	-32767 (-215+1) or less*
INT_MAX	Maximum value for an object of type int	32767 (215-1) or greater*
UINT_MAX	Maximum value for an object of type unsigned int	65535 (216-1) or greater*
LONG_MIN	Minimum value for an object of type long int	-2147483647 (-231+1) or less*
LONG_MAX	Maximum value for an object of type long int	2147483647 (231-1) or greater*
ULONG_MAX	Maximum value for an object of type unsigned long int	4294967295 (232-1) or greater*
LLONG_MIN	Minimum value for an object of type long long int	-9223372036854775807 (-263+1) or less*
LLONG_MAX	Maximum value for an object of type long long int	9223372036854775807 (263-1) or greater*
ULLONG_MAX	Maximum value for an object of type unsigned long long int	18446744073709551615 (264-1) or greater*

---

Demo

C

#include <stdio.h>
#include <limits.h>

int main() {
   printf("The value of CHAR_BIT: %d\n", CHAR_BIT);
   printf("The value of SCHAR_MIN: %d\n", SCHAR_MIN);
   printf("The value of SCHAR_MAX: %d\n", SCHAR_MAX);
   printf("The value of UCHAR_MAX: %u\n", UCHAR_MAX);
   printf("The value of CHAR_MIN: %d\n", CHAR_MIN);
   printf("The value of CHAR_MAX: %d\n", CHAR_MAX);
   printf("The value of MB_LEN_MAX: %d\n", MB_LEN_MAX);
   printf("The value of SHRT_MIN: %d\n", SHRT_MIN);
   printf("The value of SHRT_MAX: %d\n", SHRT_MAX);
   printf("The value of USHRT_MAX: %u\n", USHRT_MAX);
   printf("The value of INT_MIN: %d\n", INT_MIN);
   printf("The value of INT_MAX: %d\n", INT_MAX);
   printf("The value of UINT_MAX: %u\n", UINT_MAX);
   printf("The value of LONG_MIN: %ld\n", LONG_MIN);
   printf("The value of LONG_MAX: %ld\n", LONG_MAX);
   printf("The value of ULONG_MAX: %lu\n", ULONG_MAX);
   return 0;
}

C++

// limits.cpp -- some integer limits
#include <iostream>
#include <climits> // use limits.h for older systems
int main()
{
    using namespace std;
    int n_int = INT_MAX;      // initialize n_int to max int value
    short n_short = SHRT_MAX; // symbols defined in climits file
    long n_long = LONG_MAX;
    long long n_llong = LLONG_MAX;

    // sizeof operator yields size of type or of variable
    cout << "int is " << sizeof(int) << " bytes." << endl;
    cout << "short is " << sizeof n_short << " bytes." << endl;
    cout << "long is " << sizeof n_long << " bytes." << endl;
    cout << "long long is " << sizeof n_llong << " bytes." << endl;
    cout << endl;

    cout << "Maximum values:" << endl;
    cout << "int: " << n_int << endl;
    cout << "short: " << n_short << endl;
    cout << "long: " << n_long << endl;
    cout << "long long: " << n_llong << endl
         << endl;

    cout << "Minimum int value = " << INT_MIN << endl;
    cout << "Bits per byte = " << CHAR_BIT << endl;
    // cin.get();
    return 0;
}

// (base) kimshan@MacBook-Pro output % ./"limits"
// int is 4 bytes.
// short is 2 bytes.
// long is 8 bytes.
// long long is 8 bytes.

// Maximum values:
// int: 2147483647
// short: 32767
// long: 9223372036854775807
// long long: 9223372036854775807

// Minimum int value = -2147483648
// Bits per byte = 8

---

Resources

[1] https://cplusplus.com/reference/climits/

[2] https://www.geeksforgeeks.org/climits-limits-h-cc/