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>
  3. union student{
  4. char sname[20];
  5. }
  6. main()
  7. {
  8. union student std;
  9. puts("Enter student name : ");
  10. gets(std.sname);
  11. puts("\n------ DATA STORE COMPLETED ------\n");
  12. printf("Student Name is : %s.",std.sname);
  13. puts("\n------ DATA STORE COMPLETED ------");
  14. printf("Student Name is : %s.",std.sname);
  15. getch();
  16. }

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>
  3. union student{
  4. char username[5];
  5. char sname[20];
  6. }
  7. main()
  8. {
  9. printf("\n size of this union - %d.",sizeof(union student));
  10. getch();
  11. }

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>
  3. enum week{sunday, monday, tuesday, wednesday, thursday, friday, saturday};
  4. main()
  5. {
  6. enum week today;
  7. today = monday;
  8. printf("\n Day %d.",today+1);
  9. getch();
  10. }

Output :

c language - write a simple program use enum

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