why padding is not happening in this case?

Question

As per my knowledge, By default 4-byte alignment will be done. say

typedef struct
{
     int data7;  
     unsigned char data8;
     //3 -bytes will be added         


        

Answer 1

None of the fields in your second struct require 4-byte alignment. unsigned char only needs 1-byte alignment. Therefore, there is no need to actually align it to 4 bytes.

Structs are generally only aligned to the maximum alignment of all the fields.