c++拾遗之数据类型占用内存大小总结

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一：整形


      int                      4字节


      long int                 4字节


      short int                2字节


      unsigned int             4字节


      unsigned long int        4字节


      unsigned short int       2字节


二：字符型


      char                       1字节


      unsigned char              1字节


三：浮点型


      float                      4字节


      double                     8字节


      long double                8字节


      unsigned long double       8字节


      unsigned double            8字节


四：字符串型


      string                     16字节


五：指针类型


      所有类型的指针都是 4字节


六：函数


      除了void型。其他都函数占有的字节数等于函数的返回类型所占有的字节数。与函数体内部无关。


如：int fun(){}


      sizeof(fun()) = 4;


      int fun2(){string a;}


      sizeof(fun2()) = 4;


七：结构体、类


      内部各数据类型占用之和，然后取比这个和值最近的4的倍数。（如果本身已经是4的倍数就不用取了）


如：struct fun
    {
      string a;   //16
      char b;     //1。和为17，最近的4的倍数是20，所以sizeof（a） = 20；
    }a;


    struct fun2
    {
      string a;   //16
      char b,c,d;     //3。和为19，最近的4的倍数是20，所以sizeof（b） = 20；
    }b;


八：联合体union


      取其中占有字节数最大的数据类型所占有的字节数。

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// 32位系统中C/C++中各种类型int、long、double、char表示范围（最大最小值）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;