C、C++数据类型(int, long, short, char, long long) 的取值范围、最大最小值：climits 里的一些宏

- 日理万妓 2022-07-20 12:10 175阅读 0赞

#include <iostream>
    #include <climits>
    
    using namespace std;
    
    int main()
    {
    
        cout << "int is "       <<sizeof(int)       << " bytes." << endl;
        cout << "short is "     <<sizeof(short)     << " bytes." << endl;
        cout << "long is "      <<sizeof(long)      << " bytes." << endl;
        cout << "long long is " <<sizeof(long long) << " bytes." << endl;
        cout << endl;
    
    
        cout << "*****Maximum values:*****" << endl;
        cout << "int: "                 << INT_MAX          << endl;
        cout << "short: "               << SHRT_MAX         << endl;
        cout << "long: "                << LONG_MAX         << endl;
        cout << "long long: "           << LLONG_MAX        << endl;
        cout << "long long: "           << LONG_LONG_MAX    << endl;//和上一个相同
        cout << "char: "                << CHAR_MAX         << endl;
        cout << "signed char: "         << SCHAR_MAX        << endl;
        cout << "unsigned char: "       << CHAR_MAX         << endl;
        cout << "unsigned short: "      << USHRT_MAX        << endl;
    //    cout << "unsigned int: "        << UNIT_MAX         << endl;//报错
        cout << "unsigned long: "       << ULONG_MAX        << endl;
        cout << "unsigned long long: "  << ULLONG_MAX       << endl;
        cout << "unsigned long long: "  << ULONG_LONG_MAX   << endl;//和上一个相同
        cout << endl;
    
    
        cout << "*****Minimum values:*****" << endl;
        cout << "int: "         << INT_MIN          << endl;
        cout << "short: "       << SHRT_MIN         << endl;
        cout << "long: "        << LONG_MIN         << endl;
        cout << "long long: "   << LLONG_MIN        << endl;
        cout << "long long: "   << LONG_LONG_MIN    << endl;//和上一个相同
        cout << "char: "        << CHAR_MIN         << endl;
        cout << "signed char: " << SCHAR_MIN        << endl;
        cout << endl;
    
    
        cout<<"Bits per byte = "<<CHAR_BIT<<endl;
    
    
        return 0;
    }

64位win7运行结果
    
    int is 4 bytes.
    short is 2 bytes.
    long is 4 bytes.
    long long is 8 bytes.
    
    *****Maximum values:*****
    int: 2147483647
    short: 32767
    long: 2147483647
    long long: 9223372036854775807
    long long: 9223372036854775807
    char: 127
    signed char: 127
    unsigned char: 127
    unsigned short: 65535
    unsigned long: 4294967295
    unsigned long long: 18446744073709551615
    unsigned long long: 18446744073709551615
    
    *****Minimum values:*****
    int: -2147483648
    short: -32768
    long: -2147483648
    long long: -9223372036854775808
    long long: -9223372036854775808
    char: -128
    signed char: -128
    
    Bits per byte = 8

#include<iostream>
    #include<string>
    #include <limits>
    using namespace std;
    
    int main()
    {
        cout << "type: \t\t" << "************size**************"<< endl;
        cout << "bool: \t\t" << "所占字节数：" << sizeof(bool);
        cout << "\t最大值：" << (numeric_limits<bool>::max)();
        cout << "\t\t最小值：" << (numeric_limits<bool>::min)() << endl;
        cout << "char: \t\t" << "所占字节数：" << sizeof(char);
        cout << "\t最大值：" << (numeric_limits<char>::max)();
        cout << "\t\t最小值：" << (numeric_limits<char>::min)() << endl;
        cout << "signed char: \t" << "所占字节数：" << sizeof(signed char);
        cout << "\t最大值：" << (numeric_limits<signed char>::max)();
        cout << "\t\t最小值：" << (numeric_limits<signed char>::min)() << endl;
        cout << "unsigned char: \t" << "所占字节数：" << sizeof(unsigned char);
        cout << "\t最大值：" << (numeric_limits<unsigned char>::max)();
        cout << "\t\t最小值：" << (numeric_limits<unsigned char>::min)() << endl;
        cout << "wchar_t: \t" << "所占字节数：" << sizeof(wchar_t);
        cout << "\t最大值：" << (numeric_limits<wchar_t>::max)();
        cout << "\t\t最小值：" << (numeric_limits<wchar_t>::min)() << endl;
        cout << "short: \t\t" << "所占字节数：" << sizeof(short);
        cout << "\t最大值：" << (numeric_limits<short>::max)();
        cout << "\t\t最小值：" << (numeric_limits<short>::min)() << endl;
        cout << "int: \t\t" << "所占字节数：" << sizeof(int);
        cout << "\t最大值：" << (numeric_limits<int>::max)();
        cout << "\t最小值：" << (numeric_limits<int>::min)() << endl;
        cout << "unsigned: \t" << "所占字节数：" << sizeof(unsigned);
        cout << "\t最大值：" << (numeric_limits<unsigned>::max)();
        cout << "\t最小值：" << (numeric_limits<unsigned>::min)() << endl;
        cout << "long: \t\t" << "所占字节数：" << sizeof(long);
        cout << "\t最大值：" << (numeric_limits<long>::max)();
        cout << "\t最小值：" << (numeric_limits<long>::min)() << endl;
        cout << "unsigned long: \t" << "所占字节数：" << sizeof(unsigned long);
        cout << "\t最大值：" << (numeric_limits<unsigned long>::max)();
        cout << "\t最小值：" << (numeric_limits<unsigned long>::min)() << endl;
        cout << "double: \t" << "所占字节数：" << sizeof(double);
        cout << "\t最大值：" << (numeric_limits<double>::max)();
        cout << "\t最小值：" << (numeric_limits<double>::min)() << endl;
        cout << "long double: \t" << "所占字节数：" << sizeof(long double);
        cout << "\t最大值：" << (numeric_limits<long double>::max)();
        cout << "\t最小值：" << (numeric_limits<long double>::min)() << endl;
        cout << "float: \t\t" << "所占字节数：" << sizeof(float);
        cout << "\t最大值：" << (numeric_limits<float>::max)();
        cout << "\t最小值：" << (numeric_limits<float>::min)() << endl;
        cout << "size_t: \t" << "所占字节数：" << sizeof(size_t);
        cout << "\t最大值：" << (numeric_limits<size_t>::max)();
        cout << "\t最小值：" << (numeric_limits<size_t>::min)() << endl;
        cout << "string: \t" << "所占字节数：" << sizeof(string) << endl;
        // << "\t最大值：" << (numeric_limits<string>::max)() << "\t最小值：" << (numeric_limits<string>::min)() << endl;
        cout << "type: \t\t" << "************size**************"<< endl;
        return 0;
    }

64位win7运行结果
    type:           *****************************SIZE****************************
    bool:           所占字节数：1   最大值：1               最小值：0
    char:           所占字节数：1   最大值：               最小值：€
    signed char:    所占字节数：1   最大值：               最小值：€
    unsigned char:  所占字节数：1   最大值：              最小值：
    wchar_t:        所占字节数：2   最大值：65535           最小值：0
    short:          所占字节数：2   最大值：32767           最小值：-32768
    int:            所占字节数：4   最大值：2147483647      最小值：-2147483648
    unsigned:       所占字节数：4   最大值：4294967295      最小值：0
    long:           所占字节数：4   最大值：2147483647      最小值：-2147483648
    unsigned long:  所占字节数：4   最大值：4294967295      最小值：0
    double:         所占字节数：8   最大值：1.79769e+308    最小值：2.22507e-308
    long double:    所占字节数：12  最大值：Infinity        最小值：0
    float:          所占字节数：4   最大值：3.40282e+38     最小值：1.17549e-38
    size_t:         所占字节数：4   最大值：4294967295      最小值：0
    string:         所占字节数：4
    type:           *****************************SIZE****************************

/\*运行结果分析：

以上结果已经很明白了，一下补充说明几点：

概念、整型：表示整数、字符和布尔值的算术类型合称为整型（integral type）。

关于带符号与无符号类型：整型 int、stort  和  long 都默认为带符号型。要获得无符号型则必须制定该类型为unsigned，比如unsigned long。unsigned int类型可以简写为unsigned，也就是说，unsigned后不加其他类型说明符就意味着是unsigned int。

一字节表示八位，即：1byte = 8 bit;

int: 4byte =  32 bit有符号signed范围：2^31-1 ~ -2^31即：2147483647 ~ -2147483648无符号unsigned范围：2^32-1 ~ 0即：4294967295 ~ 0

long: 4 byte = 32 bit同int型

double: 8 byte = 64 bit范围：1.79769e+308 ~ 2.22507e-308

long double: 12 byte = 96 bit范围： 1.18973e+4932 ~ 3.3621e-4932

float: 4 byte = 32 bit范围： 3.40282e+038 ~ 1.17549e-038

int、unsigned、long、unsigned long 、double的数量级最大都只能表示为10亿，即它们表示十进制的位数不超过10个，即可以保存所有9位整数。而short只是能表示5位；

另外对于浮点说而言：使用double类型基本上不会有错。在float类型中隐式的精度损失是不能忽视的，二双精度计算的代价相对于单精度可以忽略。事实上，在有些机器上，double类型比float类型的计算要快得多。float型只能保证6位有效数字，而double型至少可以保证15位有效数字（小数点后的数位），long double型提供的精度通常没有必要，而且还要承担额外的运行代价。

double是8字节共64位，其中小数位占52位，2-^52=2.2204460492503130808472633361816e-16，量级为10^-16，故能够保证2^-15的所有精度。

在有些机器上，用long类型进行计算所付出的运行时代价远远高于用int类型进行同样计算的代价，所以算则类型前要先了解程序的细节并且比较long类型与int类型的实际运行时性能代价。