Unions :

What is Union ?

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

Syntax :

  1. union student
  2. {
  3. int roll_no;
  4. char sname[30];
  5. };

Example :

  1. /* Description: union program to store student data */
  2. #include<stdio.h>
  4. union student{
  5. char sname[20];
  6. }
  8. main()
  9. {
  10. union student std;
  12. puts("Enter student name : ");
  13. gets(std.sname);
  15. puts("\n------ DATA STORE COMPLETED ------\n");
  17. printf("Student Name is : %s.",std.sname);
  19. puts("\n------ DATA STORE COMPLETED ------");
  21. printf("Student Name is : %s.",std.sname);
  22. getch();
  23. }

Output :

c language - union program to store student data

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 :

  1. /* Description: find size of union */
  2. #include<stdio.h>
  4. union student{
  5. char username[5];
  6. char sname[20];
  7. }
  9. main()
  10. {
  11. printf("\n size of this union - %d.",sizeof(union student));
  12. getch();
  13. }

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

Output :

c language - union program to store student data

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 :

  1. /* Description: write a simple program use enum */
  2. #include<stdio.h>
  4. enum week{sunday, monday, tuesday, wednesday, thursday, friday, saturday};
  6. main()
  7. {
  8. enum week today;
  9. today = monday;
  10. printf("\n Day %d.",today+1);
  11. getch();
  12. }

Output :

c language - write a simple program use enum

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