structure

[anarghya]

how a structure is different from union?

[horace1]

how a structure is different from union?

A union is similar to a structure in the way that it is declared and how its members are accessed, but there is a fundamental difference in the way storage is allocated:

structures: each member has its own area of storage
unions: the members use the same area of storage, i.e. they overlay each other.

[baburk]

At a time u can store only one value in union. Because, all variables occupy the same memory. If u store 2 values it will affect the other variable.

[koder]

consider the code below,

#include<stdio.h>
union koder {

                  char c;
                  int i;
                  double d;
              };

main()
 {
   union  koder  new;
   printf("\n %d",sizeof(new));
}

#

#include<stdio.h
union koder {

                  char c;
                  int i;
                  double d;
              };
main()
 {
    union  koder  new;
   printf("\n %d",sizeof(new));

}

first code peice shows a union,when u print the size of the union it will give u the size of the largest member present in union .so at a time only any one member of the union can be accessed
But in second case the size of the structure gives u ,the 16 bytes(with gcc obvious) This includes the padding considerations, so equall to sum of sizes of all the element present.Thus we can understand that in a structure we can all elements or a single element.

[koder]

i mean we can access single element or all elements at a given time
Thanks