.NET内存分配

Question

请查看以下代码：

unsafe
{
   byte by = 1; // 1 byte 
   short sh = 1; // 2 bytes
   int it = 1; // 4 bytes
   double dou = 1; //8 bytes

   byte* byP = &by;
   short* shP = &sh;
   int* itP = ⁢
   double* douP = &dou;

   IntPtr add = (IntPtr)byP;
   IntPtr add2 = (IntPtr)shP;
   IntPtr add3 = (IntPtr)itP;
   IntPtr add4 = (IntPtr)douP;

   Console.WriteLine(Marshal.SizeOf(by) + " " + Marshal.SizeOf(sh) + " " + Marshal.SizeOf(it) + " " + Marshal.SizeOf(dou));
   Console.WriteLine(add.ToString() + " " + add2.ToString() + " " + add3.ToString() + " " + add4.ToString());

   //output:
   //1 2 4 8
   //--------------------------------------------------------------------
   //6943624 6943620 6943616 6943608
}

我无法理解为什么 short 或 byte 这样的类型在RAM中保留4个字节的内存，如果 short 需要2个字节且 byte 只需要1个字节吗？有人可以向我解释一下吗？