c++ sizeof() 位运算

c++ sizeof() 位运算

• sizeof() 函数是返回值的单位是 Byte，1 Byte = 8 bits.
• 目前，c++ 最长的数值类型可以有 64 位。

 

#include <iostream>
#include <climits>

int main()
{
   unsigned long long int a = 1;    /* 1 = 0000 0001 */
   unsigned long long int b = 0;
   // unsigned long long int c = pow(2,64) - 1;           

   b = a << 63;     /*4  = 0000 0000 */
   std::cout << "b = " << b << std::endl;

   std::cout << "size of int = " << sizeof(int) << std::endl;
   std::cout << "size of unsigned long long int = " << sizeof(unsigned long long int) << std::endl;

   return 0;
}

out

b = 9223372036854775808
size of int = 4
size of unsigned long long int = 8