What is Union ?

Similar to a structure, a union also consists of data members but only one data is active at a time.

Syntax :

union student { int roll_no; char sname[30]; };

Example :

/* Description: union program to store student data */ #include<stdio.h> union student{ char sname[20]; } main() { union student std; puts("Enter student name : "); gets(std.sname); puts("\n------ DATA STORE COMPLETED ------\n"); printf("Student Name is : %s.",std.sname); puts("\n------ DATA STORE COMPLETED ------"); printf("Student Name is : %s.",std.sname); getch(); }

Output :

sizeof() of a union :

sizeof() a union is equal to the number of bytes occupied in RAM by the largest data member in the union.

Example :

/* Description: find size of union */ #include<stdio.h> union student{ char username[5]; char sname[20]; } main() { printf("\n size of this union - %d.",sizeof(union student)); getch(); }

The size of this union equal 20bytes because the largest data member sname occupies 20bytes in RAM.

Output :

enum :

enum represents the enumeration data type which is used to instruct the compiler to associate with the specific list of values for a variables.

Example :

/* Description: write a simple program use enum */ #include<stdio.h> enum week{sunday, monday, tuesday, wednesday, thursday, friday, saturday}; main() { enum week today; today = monday; printf("\n Day %d.",today+1); getch(); }

Output :