CALCULATING THE SIZE OF STRUCTURE IN C/C++:

consider a strucure

struct X
{
    short s; 
    int   i; 
    char  c; 
             
};

what do you think the size of structure will be? 2 + 4 + 1 ?

Sorry, then you are wrong. Because to reduce the lookup time by CPU compiler pads up the bytes untill it becomes a multiple of 4. This is however dependent on hardware,but most compilers does so.

so what happens is 

struct X
{
    short s; /* 2 bytes */
             /* 2 padding bytes */
    int   i; /* 4 bytes */
    char  c; /* 1 byte */
             /* 3 padding bytes */
};

but this is not the best way to declare the struct , why? because you waste space due to  padding of bytes. So here are some tricks to reduce the eat up of byte padding







struct Y
{
    int   i; /* 4 bytes */
    char  c; /* 1 byte */
             /* 1 padding byte */
    short s; /* 2 bytes */
};

struct Z
{
    int   i; /* 4 bytes */
    short s; /* 2 bytes */
    char  c; /* 1 byte */
             /* 1 padding byte */
};

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