12 bytes, four bytes for each of three integers.
A block of memory for this struct consists of twelve bytes.
The first field (age) is located at a displacement of
zero into the block.
The second field (pay) is located at a displacement of
four into the block.
The last field (class) is located at a displacement of
eight into the block.
struct
{
int age;
int pay;
int class;
} myData ;