Size of a struct in C

Question

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What is the actual size of a struct in C

I wrote the following program in C and I'm a little confused about the size of the struct that the executable prints. Here is the code:

#include <stdio.h>
#include <stdlib.h>

struct domi1{
   char x;
   int c;
   char y;
};

struct domi2{
   char x;
   char y;
   int c;
};

main(){

 printf("The size of domi1 is: %d\n", sizeof(struct domi1));
 printf("The size of domi2 is: %d\n\n", sizeof(struct domi2));

 system("pause");
}

The program prints 12 as the size of domi1 and 8 as the size of domi2. Why is that? I appreciate your help!

score -1 · Accepted Answer · answered Oct 20 '12 at 14:24

-1

because of Packing and byte alignment
The general answer is that compilers are free to add padding between members for alignment purpose. or we can say that, You might have a compiler that aligns everything to 8 bytes. first struct assigned memory as- 4 4 4
second struct- single 4 for both char and 4 for int

answered Oct 20 '12 at 14:24

Ravindra Bagale

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Thanks for your response!!quite helped me.. – mgus Oct 20 '12 at 15:05
I don't think this is the complete answer – Omkant Oct 20 '12 at 17:29
Actually memory is aligned according to the sizeof largest datatype – Omkant Oct 20 '12 at 17:31
for actual clarification use "double" in your struct and just check with the different order of declaration sequence you will get it – Omkant Oct 20 '12 at 17:32

Size of a struct in C

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