union vs structure

This page on union vs structure describes difference between union and structure. Both structure and union store more than one variables of the different data type. Difference lies in the way these variables are allocated memory in both the cases. Let us understand the concept with following example c program.

struct emp_record
{ char name[10];
int number[12];
float Salary;

union emp_record
char name[10];
int number[12];
float Salary;

For structure, total memory allocated is about 7 bytes, which include 1 byte for char,2 for int and 4 for float. In structure all the member variables are stored consecutively one after the other. For union, total memory allocated is about 4 bytes, which will be shared by all the variables at different time instants. In union total size is allocated equal to size of the maximum size of the member variable.


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