what is aligned and unaligned data in c

[bhrugu]

what is aligned and unaligned data in c and what's the use of it.

[bithub]

The compiler will align variables depending on architecture requirements, or just to improve performance. For a code illustration, run the following:

#include <stdio.h>

struct s
{
    char c;
    int i;
};

int main(void)
{
    printf("size: %u\n", sizeof(struct s));
    return 0;
}

If you your machine uses 4 byte integers (like most machines), then you might expect the structure to be a size of 5 in the above code. Chances are that if you compile and run that, you will get 8 bytes as the result. Why? Because the compiler aligns the integer on 4 byte boundaries, so there are 3 unused bytes between the character and the integer.