Module 5 - Pointer,Structures and Union.pptm.pdf

pointers in c

1. PRPEARED BY: PROF. NEHA HARDE ©
C PROGRAMMING
Module 5

Structure,Union and Pointer
Course Outcome (CO5):
Demonstrate the use of structure and union in C language

2. PRPEARED BY: PROF. NEHA HARDE ©
❖Introduction of structure
❖Structure Declaration
❖Structure Variable
❖Structure Variable Initialization
❖Structure elements in memory
❖Structure Example
❖Typedef
❖Array of structures
❖Nested Structure
❖Passing Structure to function
❖Assigning value of one structure to another







Structure

3. PRPEARED BY: PROF. NEHA HARDE ©
INTRODUCTION OF STRUCTURE
Array is used to store several elements of same type
eg. Roll no. of students can be stored in an array of type int
int roll_no[60];

Problem Statement:
Store students information like roll no., name, department, college, marks
Roll No. – int
Name – char[10]
Department – char[5]
Marks – float

There are two approaches:
1.Construct individual arrays, one for roll no, one for name, one for class…..
2.Use a structure

4. PRPEARED BY: PROF. NEHA HARDE ©
STRUCTURE DECLARATION
Defining a structure:
Each element in a structure is called as member
struct structure_name
{
structure element 1;
structure element 2;
structure element 3;
.
.
.
};
Syntax
struct student
{
int roll_no;
char student_name[10];
char dept[10];
float marks;
};
Example
Structure is a user defined data type that can hold different types of data together in a single type

5. PRPEARED BY: PROF. NEHA HARDE ©
STRUCTURE VARIABLE
❖Structure is user defined data type, variables of that type can be declared
Different ways to declare variables are -


struct student
{
int roll_no;
char student_name[10];
char dept[5];
float marks;
}s1, s2, *s3;
struct student
{
int roll_no;
char student_name[10];
char dept[5];
float marks;
};
struct student s1;
struct student s2;

struct student
{
int roll_no;
char student_name[10];
char dept[5];
float marks;
};
struct student s1, s2;

6. PRPEARED BY: PROF. NEHA HARDE ©
STRUCTURE VARIABLE INITIALIZATION
struct student
{
int roll_no;
char student_name[10];
char dept[5];
float marks;
};
struct student s1={10, ”Neha”, “IT” 90.50};
struct student s2={12, “Ram”, “Comp”, 85.00};
struct student s3 = {0};
❖Structure elements can be accessed using dot
operator

Syntax:
structureVariable.structureElement
Example:
s1.roll_no
s1.dept

7. PRPEARED BY: PROF. NEHA HARDE ©
STRUCTURE ELEMENTS IN
MEMORY
struct student
{
int roll_no;
char student_name[10];
char dept[5];
float marks;
};
struct student s1={10, ”Neha”, “IT”, 90.50};

100 104 114 119
s1.roll_no s1.student_name s1.dept s1.marks
123

8. PRPEARED BY: PROF. NEHA HARDE ©
STRUCTURE EXAMPLE
Problem statement: Define structure student with members roll_no, student_name,
dept, marks and accept student record from user and display student record.









struct student
{
int roll_no;
char student_name[10];
char dept[5];
float marks;
};
struct student s1={10, ”Neha”, “IT”, 90.50};

int main()
{
struct student s2;
printf(“\n Enter s2 information:”);
scanf(“%d %s %s %f”, &s2.roll_no, s2.student_name, s2.dept, &s2.marks);
printf(“\n Displaying s1 record: %d %s %s %.2f”, s1.roll_no, s1.student_name, s1.dept,s1.marks);
printf(“\n Displaying s2 record: %d %s %s %.2f”, s2.roll_no, s2.student_name, s2.dept,s2.marks);
return 0;
}

9. PRPEARED BY: PROF. NEHA HARDE ©
TYPEDEF
❖typedef is a keyword used to assign alternative names to existing datatypes
❖It is mostly used with user defined data types, when names of the data types become complicated to use in programs
Syntax: typedef existing_datatype new_datatype









struct student
{
int roll_no;
char student_name[10];
char dept[10];
float marks;
};
struct student s1={10, ”Neha”, “IT”, 90.50};
struct student s2={12, “Ram”, “Comp”, 85.00};
typedef struct student
{
int roll_no;
char student_name[10];
char dept[10];
float marks;
}stud;
stud s1={10, ”Neha”, “IT”, 90.50};
stud s2={12, “Ram”, “Comp”, 85.00};
Old Data type
New Data type

10. PRPEARED BY: PROF. NEHA HARDE ©
TYPEDEF
Problem statement: Define structure student with members roll_no, student_name,
dept, marks and accept student record from user and display student record.









typedef struct student
{
int roll_no;
char student_name[10];
char dept[5];
float marks;
}stud;
stud s1={10, ”Neha”, “IT”, 90.50};

int main()
{
stud s2;
printf(“\n Enter s2 information:”);
scanf(“%d %s %s %f”, &s2.roll_no, s2.student_name, s2.dept, &s2.marks);
printf(“\n Displaying s1 record: %d %s %s %.2f”, s1.roll_no, s1.student_name, s1.dept,s1.marks);
printf(“\n Displaying s2 record: %d %s %s %.2f”, s2.roll_no, s2.student_name, s2.dept,s2.marks);
return 0;
}

11. PRPEARED BY: PROF. NEHA HARDE ©
ARRAY OF STRUCTURES
Problem Statement: Store information of 60 students and print it.
Solution: Use Array of Structure






struct student
{
int roll_no;
char student_name[10];
char dept[10];
float marks;
};
struct student s1={10, ”Neha”, “IT”, 90.50};
struct student s2={12, “Ram”, “Comp”, 85.00};
…….
typedef struct student
{
int roll_no;
char student_name[10];
char dept[10];
float marks;
}stud s[60];

12. PRPEARED BY: PROF. NEHA HARDE ©
ARRAY OF STRUCTURES

S[0].roll_no S[0].student_name S[0].dept S[0].marks

S[1].roll_no S[1].student_name S[1].dept S[1].marks

S[2].roll_no S[2].student_name S[2].dept S[2].marks

13. PRPEARED BY: PROF. NEHA HARDE ©
ARRAY OF STRUCTURES
typedef struct student
{
int roll_no;
char student_name[10];
char dept[5];
float marks;
}stud;
stud s[5];

int main()
{
int i;
printf(“\n Enter Student information:”);
for(i=0; i<5; i++)
{
printf(“\n Enter values of s[%d] record: ”, i+1);
scanf(“%d %s %s %f”, &s[i].roll_no, s[i].student_name, s[i].dept, &s[i].marks);
printf(“\n Displaying s[%d] record: %d %s %s %.2f”, i+1, s[i].roll_no, s[i].student_name, s[i].dept, s[i].marks);
}
return 0;
}

14. PRPEARED BY: PROF. NEHA HARDE ©
NESTED STRUCTURES









Print student s1 record:
printf(“Roll no = %d Name= %s Dept = %s Marks = %.2f City = %s Pin = %d ”, s1.roll_no, s1.student_name, s1.dept, s1.marks,
s1.add.city, s1.add.pin);







struct address
{
char city[10];
int pin;
};

struct address add;

struct student
{
int roll_no;
char student_name[10];
char dept[10];
float marks;
struct address add;
};
struct student s1 = {10, “Neha”, “IT”, 90.50, “Mumbai”, 400011};

15. PRPEARED BY: PROF. NEHA HARDE ©
NESTED STRUCTURES
struct address
{
char city[10];
int pin;
};
struct address add;

struct student
{
int roll_no;
char student_name[10];
char dept[10];
float marks;
struct address add;
};
struct student s1 = {10, “Neha”, “IT”, 90.50, “Mumbai”, 400011}

int main()
{
printf(“\n Displaying s1 record: ”);
printf(“\n %d %s %s %f %s %d”, s1.roll_no, s1.student_name, s1.dept, s1.marks, s1.add.city, s1.add.pin);
return 0;
}

16. PRPEARED BY: PROF. NEHA HARDE ©
PASSING STRUCTURE TO FUNCTION
Two ways to pass structure to a function
❖Passing individual structure members to a function

❖Passing an entire structure to a function

17. PRPEARED BY: PROF. NEHA HARDE ©
PASSING INDIVIDUAL MEMBER TO A FUNCTION
#include<stdio.h>
typedef struct student
{
int rollno;
char name[20];
float marks;
}stud;
int main()
{
stud s1 = {11, “Mohit”, 98.7};
printf("\nDisplay student information\n");
display(s1.rollno, s1.name, s1.marks); return 0;
}
void display(int r, char n[20], float m)
{
printf("%d %s %f ",r, n, m);
}

18. PRPEARED BY: PROF. NEHA HARDE ©
PASSING ENTIRE STRUCTURE TO A FUNCTION
#include<stdio.h>
typedef struct student
{
int rollno;
char name[20];
float marks;
}stud;
int main()
{
stud s1 = {11, “Mohit”, 98.7};
printf("\nDisplay student information\n");
display(s1);
return 0;
}
void display(stud s)
{
printf("%d %s %f ",s.rollno, s.name, s.marks);
}

19. PRPEARED BY: PROF. NEHA HARDE ©
PASSING ENTIRE STRUCTURE TO A FUNCTION
typedef struct student
{
int rollno;
char name[20];
float marks;
}stud s1;

stud *ptr = &s1;
Structure and Pointer
❖Structure members can be accessed using arrow
operator (->) when they are accessed by pointer

20. PRPEARED BY: PROF. NEHA HARDE ©
PASSING ENTIRE STRUCTURE TO A FUNCTION
#include<stdio.h>
typedef struct student
{
int rollno;
char name[20];
float marks;
}stud;
int main()
{
stud s1 = {11, “Mohit”, 98.7};
printf("\nDisplay student information\n");
display(&s1);
return 0;
}
void display(stud *ptr)
{
printf("%d %s %f ",ptr->rollno, ptr->name, ptr->marks);
}
Structure and Pointer

21. PRPEARED BY: PROF. NEHA HARDE ©
ASSIGNING VALUE OF ONE STRUCTURE TO ANOTHER
typedef struct student
{
int rollno;
char name[20];
float marks;
}stud s1,s2,s3;
stud s1 = {1, “naina”, 80.5};
❖Assigning all elements at a time:
s2 = s1;

❖Assigning one elements value at a time:
s3.rollno = s1.rollno;
strcpy(s3.name,s1.name);
S3.marks = s1.marks;

22. PRPEARED BY: PROF. NEHA HARDE ©
❖Introduction of Union
❖Union variable
❖Accessing union members
❖Memory allocation
❖Union example
❖Structure vs Union


Union

23. PRPEARED BY: PROF. NEHA HARDE ©
INTRODUCTION OF UNION
Union is a user-defined data type which can hold collection
of different type of data in the same memory location
Defining a union:
union keyword is used for defining a union having members of different type
union union_name
{
union element 1;
union element 2;
union element 3;
.
.
.
};
Syntax
union student
{
int roll_no;
char student_name[10];
char dept[10];
float marks;
};
Example

24. PRPEARED BY: PROF. NEHA HARDE ©
UNION VARIABLE
❖Union is user defined data type, variables of that type can be declared
Different ways to declare variables are -


union student
{
int roll_no;
char student_name[10];
char dept[5];
float marks;
}s1, s2, s3;
union student
{
int roll_no;
char student_name[10];
char dept[5];
float marks;
};
union student s1;
union student s2;

union student
{
int roll_no;
char student_name[10];
char dept[5];
float marks;
};
union student s1, s2;

25. PRPEARED BY: PROF. NEHA HARDE ©
ACCESSING UNION MEMBERS
union student
{
int roll_no;
char student_name[10];
char dept[5];
float marks;
};
union student s1, *s2;
❖Union elements can be accessed using dot operator (Using Variable s1)
Syntax: unionVariable.unionElement
Example:
s1.roll_no
s1.dept
❖Union elements can be accessed using arrow operator
(Using Pointer variable *s2)
Syntax: unionVariable->unionElement
Example:
s2->roll_no
s2->dept

26. PRPEARED BY: PROF. NEHA HARDE ©
MEMORY ALLOCATION
❖Memory is not allocated while defining a union but it is allocated while declaring a variable of union
❖All union elements share same memory
❖Memory equal to the size of largest element is allotted to union
❖Union can contain different types of elements but not all elements can be initialized at a time
❖Only one element can be accessed at a time
union student
{
int roll_no;
char student_name[10];
char dept[5];
float marks;
};

101
student_name = 10 bytes
110

27. PRPEARED BY: PROF. NEHA HARDE ©
UNION EXAMPE
union student
{
int roll_no;
char student_name[10];
};

int main()
{
union student s2;
printf(“\n Enter rollno:”);
scanf(“%d”, &s2.roll_no);
printf(“%d”, s2.roll_no);
printf(“\n Enter name”);
scanf(“%s”, s2.student_name);
printf(“%s”, s2.student_name);
return 0;
}

Invalid Initialization:

union student s1={10, “Neha”};

28. PRPEARED BY: PROF. NEHA HARDE ©
STRCTURE VS UNION
union student
{
char name[40];
int roll_no;
int phone_number
};
struct student
{
char name[40];
int roll_no;
int phone_number
};

29. PRPEARED BY: PROF. NEHA HARDE ©
STRCTURE VS UNION