"Allocating the memory for a structure variable more then the required memory is called structure padding, that extra byte of memory is called hole in a structure;"
Some more examples:
struct A
{
int a;
char c;
float f;
};
Size of struct A should be 9 but it is 12, that is known as structure padding and extra 3 byte are known as hole.
For removing the hole we can use below keyword:
#pragma pack(1) //only in GCC compiler
