Union within Structure

Union within Structure

#include<stdio.h>

#include<stdlib.h>

#include<string.h>

struct student

{

            int marks;

            union

            {

                        char name[20];

                        int usn;

            } u;

} s;

main()

{

            int  ch;

            printf("\n Enter marks:");

            scanf("%d", &s.marks);

            printf("\nName or USN choice:");

            printf("\n 1.Name 2.USN: ");

            scanf("%d", &ch);

            switch(ch)

            {

                        case 1:             printf("\nEnter name:");

                                                scanf("%s", s.u.name);

                                                printf("\nYour name is:%s", s.u.name);

                                                break;

                        case 2:             printf("\nEnter usn:");

                                                scanf("%d", &s.u.usn);

                                                printf("\nYour usn is:%d", s.u.usn);

                                                break;

            }

            printf("\nYour marks is:%d", s.marks);

}

Output:

Enter marks: 80

Name or USN choice:

1.Name 2.USN:            1

Enter name: AAAAA

Your name is: AAAAA

Your marks is: 80 

Structure and Union Initialization

Structure and Union Initialization

#include<stdio.h>

struct first

{

            int x, y;

};

union second

{

            int x, y;

};

main()

{

            struct first f1 = {1, 2};

            printf("\nf1.x = %d \t f1.y = %d", f1.x, f1.y);

            union second s1;

            s1.x = 3;

            printf("\ns1.x = %d\t", s1.x);

            s1.y = 4;

            printf("\ns1.y = %d", s1.y);

            union second s2 = {6, 7};

            printf("\ns2.x = %d\t s2.y = %d", s2.x, s2.y);

            union second s3;

            s3.x = 10;

            s3.y = 9;

            printf("\ns3.x = %d\t s3.y = %d", s3.x, s3.y);

}

Output:

f1.x = 1   f1.y = 2

s1.x = 3   s1.y = 4

s2.x = 6   s2.y = 6

s3.x = 9   s3.y = 9

Unions

Module 1: Unions

• The size and address of union

• Union Initialization

• Union Example

The Size and Address of Unions

The Size and Address of Structure and Unions

#include<stdio.h>

#include<stdlib.h>

struct stag

{

            char c;

            int i;

            float f;

            double d;

};

union utag

{

            char c;

            int i;

            float f;

            double d;

};

main()

{

            struct stag s;

            printf("\n size of structure=%u", sizeof(struct stag));

            printf("\n size of structure=%u", sizeof(s));

            printf("\n address of structure=%u", &s);

            printf("\n address of structure members: %u %u %u %u", &s.c, &s.i, &s.f, &s.d);

            union utag u;

            printf("\n size of union=%u",sizeof(union utag));

            printf("\n size of union=%u",sizeof(u));

            printf("\n address of union=%u",&u);

            printf("\n address of union members: %u %u %u %u",&u.c,&u.i,&u.f,&u.d);

}

Output:

 size of structure=24

 size of structure=24

 address of structure=2686752

 address of structure members: 2686752      2686756          2686760          2686768

 size of union=8

 size of union=8

 address of union=2686744

 address of union members: 2686744            2686744          2686744          2686744

Passing Address of Structure Variable to Function

Passing Address of Structure Variable to Function

#include<stdio.h>

void display(struct student *p);

struct student

{

            char name[20];

            int rollno;

            float mark;

};

int main()

{

            struct student S1;

            printf("\nEnter name rollno and mark of a student:");

            scanf("%s %d %f", S1.name, &S1.rollno, &S1.mark );

            display(&S1);

}

void display(struct student *p)

{

    printf("\n Name is %s \n Rollno is %d \n Mark is %f", p->name, p->rollno, p->mark );

}

Output:

Enter name rollno and mark of a student: aaa 11 80

 Name is aaa

 Rollno is 11

 Mark is 80.000000

Passing Structure Variable to Function

Passing Structure Variable to Function

#include<stdio.h>

void display(struct student);

struct student

{

            char name[20];           int rollno;        float mark;

};

void main()

{

            struct student S1;

            printf("\nEnter name rollno and mark of a student:");

            scanf("%s %d %f", S1.name, &S1.rollno, &S1.mark );

            display(S1);

}

void display(struct student stu)

{

            printf("\n Name is %s \n Rollno is %d \n Mark is %f", stu.name, stu.rollno, stu.mark );

}

Output:

Enter name rollno and mark of a student: aaa 11 80

 Name is aaa

 Rollno is 11

 Mark is 80.000000

Passing Individual Structure Members to Function

Passing Individual Structure Members to Function

#include<stdio.h>

void display(char nam[], int roll, float mrk);

struct student

{

            char name[20];

            int rollno;

            float mark;

};

main()

{

            struct student S1;

            printf("\nEnter name rollno and mark of a student:");

            scanf("%s %d %f", S1.name, &S1.rollno, &S1.mark );

            display(S1.name, S1.rollno, S1.mark );

}

void display(char nam[], int roll, float mrk)

{

            printf("\n Name is %s \n Rollno is %d \n Mark is %f", nam, roll, mrk );

}

Output:

Enter name rollno and mark of a student:     aaa          11        80

 Name is aaa

 Rollno is 11

 Mark is 80.000000


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Structures and Pointers

Structures and Pointers

#include<stdio.h>

struct student

{

            char name[20];

            int rollno;

            float mark;

};

main()

{

            struct student   S1;

            struct student   *p;

            p = &S1;

            printf("\nEnter name rollno and mark of a student:");

            scanf("%s %d %f", p->name, &p->rollno, &p->mark );

            printf("\n Name is %s \n Rollno is %d \n Mark is %f", p->name, p->rollno, p->mark );

}

Output:

Enter name rollno and mark of a student: aaa 21 98

Name is aaa

Rollno is 21

Mark is 98.000000

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Array of Structures

Array of Structures

#include<stdio.h>

struct student

{

            char name[20];          
            int rollno;           
            float mark;

};

main()

{

            struct student S[10];

            int i, n;

            printf("\nEnter the number of students: ");

            scanf("%d", &n);

            for(i=0; i<n; i++)

            {

                    printf("\nEnter name rollno and mark of a student %d: ", i+1);

                        scanf("%s %d %f", S[i].name, &S[i].rollno, &S[i].mark );

            }

            for(i=0; i<n; i++)

            {

                        printf("\nStudent %d details: ", i+1);

                        printf("\n \tName is %s \n\tRollno is %d \n\tMark is %f", S[i].name, S[i].rollno, S[i].mark );

            }

}

Output:

Enter the number of students: 3

Enter name rollno and mark of a student 1: aaa       10        55

Enter name rollno and mark of a student 2: bbb       20        66

Enter name rollno and mark of a student 3: ccc        30        77

Student 1 details:

    Name is aaa

    Rollno is 10

    Mark is 55.000000

Student 2 details:

    Name is bbb

    Rollno is 20

    Mark is 66.000000

Student 3 details:

    Name is ccc

    Rollno is 30

    Mark is 77.000000


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Initialization of Structure Variables

Structure Variable Initialization

#include<stdio.h>
struct student
{
char name[20];
    int rollno;
    float mark;
}S1={"aaaa", 111, 40};                                          // Method 1 


void main()
{
     struct student S2 = {"BBB", 222, 50};         // Method 2

    struct student S3, S4, S5;

    printf("\n\n Student1: \n\tName is %s \n\tRollno is %d \n\tMark is %f", S1.name, S1.rollno,  S1.mark );
    printf("\n\n Student2: \n\tName is %s \n\tRollno is %d \n\tMark is %f", S2.name, S2.rollno, S2.mark );

    S3 = S2;                // Method 3: Assigning one structure variable to another
    printf("\n\n Student3: \n\tName is %s \n\tRollno is %d \n\tMark is %f", S3.name, S3.rollno, S3.mark );

         // Method 4: Individual members initialization
          strcpy(S4.name, "DDD");
          S4.rollno = 444;
          S4.mark = 70;
          printf("\n\n Student4: \n\tName is %s \n\tRollno is %d \n\tMark is %f", S4.name, S4.rollno, S4.mark );

         // Method 5: Taking values from user
    printf("\nEnter name rollno and mark of a student5:");
    scanf("%s %d %f", S5.name, &S5.rollno, &S5.mark );
    printf("\n\n Student5: \n\tName is %s \n\tRollno is %d \n\tMark is %f", S5.name, S5.rollno, S5.mark );

}

Output:

 Student1:
        Name is aaaa
        Rollno is 111
        Mark is 40.000000

 Student2:
        Name is BBB
        Rollno is 222
        Mark is 50.000000

 Student3:
        Name is BBB
        Rollno is 222
        Mark is 50.000000

 Student4:
        Name is DDD
        Rollno is 444
        Mark is 70.000000

Enter name rollno and mark of a student5:       EEE       555          70
Student5:
        Name is EEE
        Rollno is 555
        Mark is 70.000000


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Declaring Structure Variables

Structure Variable Declaration

1.  With structure definition

    Syntax:

     struct   tagname
    {
          datatype member1;
          datatype member2;
          :
          :
          datatype memberN;
     } var1, var2, var3 ;

     Example:

     struct  student

     {

            char  name[20];

            char usn[20];

            int age;

            float mark;

     } S1, S2, S3;  

---------------------------------------------------------------------------------------------------------------------

2.  Omitting tagname

    Syntax:

   struct   
   {
          datatype member1;
          datatype member2;
          :
          :
          datatype memberN;
   } var1, var2, var3 ;


   Example:

   struct  

   {

           char  name[20];

           char usn[20];

           int age;

           float mark;

   }S1, S2, S3;  

  

---------------------------------------------------------------------------------------------------------------------

3. Using struct tagname

    Syntax:

    struct   tagname

   {

          datatype member1;

          datatype member2;

          :

          :

          datatype memberN;

   };

   struct tagname var1, var2, var3 ;

   Example:

   struct  student

   {

         char  name[20];

         char usn[20];

         int age;

         float mark;

    };

    struct student S1, S2, S3;  

---------------------------------------------------------------------------------------------------------------------

4. Using typedef

    Syntax:

    struct   tagname

   {

          datatype member1;

          datatype member2;

          :

          :

          datatype memberN;

   };

   typedef struct tagname newname;

   newname var1, var2, var3 ;

  Example:

   struct  student

   {

         char  name[20];

         char usn[20];

         int age;

         float mark;

    };

   typedef struct student stu;

   stu S1, S2, S3;  

---------------------------------------------------------------------------------------------------------------------

5. Using typedef struct tagname

    Syntax:

   typedef struct   tagname

   {

          datatype member1;

          datatype member2;

          :

          :

          datatype memberN;

   }newname;

   newname var1, var2, var3 ;

  Example:

   typedef struct student

   {

         char  name[20];

         char usn[20];

         int age;

         float mark;

    }stu;

   stu S1, S2, S3;  

---------------------------------------------------------------------------------------------------------------------

6. Using typedef struct 

    Syntax:

   typedef struct 

   {

          datatype member1;

          datatype member2;

          :

          :

          datatype memberN;

   }newname;

   newname var1, var2, var3 ;

  Example:

   typedef struct 

   {

         char  name[20];

         char usn[20];

         int age;

         float mark;

    }stu;

   stu S1, S2, S3;  

---------------------------------------------------------------------------------------------------------------------

7. Using typedef struct tagname (omiting newname)

    Syntax:

   typedef struct tagname

   {

          datatype member1;

          datatype member2;

          :

          :

          datatype memberN;

   };

   tagname   var1, var2, var3 ;

  Example:

   typedef struct student

   {

         char  name[20];

         char usn[20];

         int age;

         float mark;

    };

   student S1, S2, S3;  

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