Difference Between Structure and Union

In this post, we will understand the difference between structure and union.

Structure

• The ‘struct’ keyword is used to define a structure.

• Every member in the structure is provided with a unique memory location.

• When the value of one data member is changed, it doesn’t affect other data members in structure.

• It helps initialize multiple members at once.

• Total size of the structure is equivalent to the sum of the size of every data member.

• It is used to store various data types.

• It takes memory for every member which is present within the structure.

• A member can be retrieved at a time.

• It supports flexible arrays.

Following is the syntax of Structure Definition −

struct [structure tag] {
   member definition;
   member definition;
   ...
   member definition;
} [one or more structure variables];

Union

• The ‘union’ keyword is used to define a union.

• A memory location is shared by all of its data members.

• Changing the value of one data member will affect/change the value of other data members as well.

• It allows the user to initialize the first member of union only.

• Total size of the union is equivalent to the size of the largest data member in the union.

• It is used to store one of the multiple data types available.

• It takes memory for a member that has the highest size.

• Only one member can be accessed at a time.

• It doesn’t support flexible arrays.

Following is the syntax of Union Definition −

union [union tag] {
   member definition;
   member definition;
   ...
   member definition;
} [one or more union variables];