Difference between structure and union
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Structure and union differ in how they allocate memory and access members. Structure allocates memory for all members and allows accessing all members at any time, while union allocates space for the largest member and only allows accessing one member at a time. Both use struct and union keywords respectively to declare them, with struct defining elements and union defining a single element that shares the same memory space.
![Difference Between Structure and Union :
Structure Union
i. Access Members
We can access all the members of
structure at anytime.
Only one member of union can be accessed at
anytime.
ii. Memory Allocation
Memory is allocated for all variables.
Allocates memory for variable which variable
require more memory.
iii. Initialization
All members of structure can be
initialized
Only the first member of a union can be initialized.
iv. Keyword
'struct' keyword is used to declare
structure.
'union' keyword is used to declare union.
v. Syntax
struct struct_name
{
structure element 1;
structure element 2;
----------
----------
structure element n;
}struct_var_nm;
union union_name
{
union element 1;
union element 2;
----------
----------
union element n;
}union_var_nm;
vi. Example
struct item_mst
{
int rno;
char nm[50];
}it;
union item_mst
{
int rno;
char nm[50];
}it;](https://image.slidesharecdn.com/differencebetweenstructureandunion-170327180205/85/Difference-between-structure-and-union-1-320.jpg)
Difference between structure and union
- 1. Difference Between Structure and Union : Structure Union i. Access Members We can access all the members of structure at anytime. Only one member of union can be accessed at anytime. ii. Memory Allocation Memory is allocated for all variables. Allocates memory for variable which variable require more memory. iii. Initialization All members of structure can be initialized Only the first member of a union can be initialized. iv. Keyword 'struct' keyword is used to declare structure. 'union' keyword is used to declare union. v. Syntax struct struct_name { structure element 1; structure element 2; ---------- ---------- structure element n; }struct_var_nm; union union_name { union element 1; union element 2; ---------- ---------- union element n; }union_var_nm; vi. Example struct item_mst { int rno; char nm[50]; }it; union item_mst { int rno; char nm[50]; }it;
- 2. Fig.: Difference between Structure and Union