Introduction-to-structures-using-C-programming.ppt

2
What is a Structure?
 Used for handling a group of logically
related data items
Examples:
 Student name, roll number, and marks
 Real part and complex part of a complex number
 Helps in organizing complex data in a more
meaningful way
 The individual structure elements are called
members

3
Defining a Structure
struct tag {
member 1;
member 2;
:
member m;
};
 struct is the required C keyword
 tag is the name of the structure
 member 1, member 2, … are individual member
declarations

4
Contd.
 The individual members can be ordinary variables,
pointers, arrays, or other structures (any data type)
 The member names within a particular structure
must be distinct from one another
 A member name can be the same as the name of
a variable defined outside of the structure
 Once a structure has been defined, the individual
structure-type variables can be declared as:
struct tag var_1, var_2, …, var_n;

5
Example
 A structure definition
struct student {
char name[30];
int roll_number;
int total_marks;
char dob[10];
};
 Defining structure variables:
struct student a1, a2, a3;
A new data-type

6
A Compact Form
 It is possible to combine the declaration of the structure
with that of the structure variables:
struct tag {
member 1;
member 2;
:
member m;
} var_1, var_2,…, var_n;
 Declares three variables of type struct tag
 In this form, tag is optional

7
Initialization of Structures

8
Structure Initialization
 Structure variables may be initialized following
similar rules of an array. The values are provided
within the second braces separated by commas
 An example:
struct complex a={1.0,2.0}, b={-3.0,4.0};
a.real=1.0; a.imag=2.0;
b.real=-3.0; b.imag=4.0;

9
Accessing a Structure
 The members of a structure are processed
individually, as separate entities
 Each member is a separate variable
 A structure member can be accessed by writing
variable.member
where variable refers to the name of a structure-type
variable, and member refers to the name of a
member within the structure
 Examples:
a1.name, a2.name, a1.roll_number, a3.dob

10
Example: Complex number addition
void main()
{
struct complex
{
float real;
float cmplex;
} a, b, c;
scanf (“%f %f”, &a.real, &a.cmplex);
scanf (“%f %f”, &b.real, &b.cmplex);
c.real = a.real + b.real;
c.cmplex = a.cmplex + b.cmplex;
printf (“n %f + %f j”, c.real, c.cmplex);
}

11
Operations on Structure
Variables
 Unlike arrays, a structure variable can be directly
assigned to another structure variable of the same type
a1 = a2;
 All the individual members get assigned
 Two structure variables can not be compared for
equality or inequality
if (a1 == a2)…… this cannot be done

12
#include<stdio.h>
struct
employee
{
int emp_id;
char name[10];
double salary;
char designation [20];
float experience;
};
void main()
{
struct employee e;
printf(“%d”,sizeof(e));
}

13
: C program to read and display the student details using structures.
#include<stdio.h>
struct student
{
int rnum;
char name[20];int marks;
}s[60];
void main()
{
int i,n;
printf("Enter the number of students");
scanf("%d",&n); printf("nEnter the roll number, Name , Marksn");
for(i=1;i<=n;i++)
{
printf("nStudent %d detailsn",i);
scanf("%d",&s[i].rnum);
scanf("%s",s[i].name);
scanf("%d",&s[i].marks);
}
printf("nStudent Details are:");
printf("nRoll_numbertNametMarks");
for(i=1;i<=n;i++)
printf("n%dtt%st%dn",s[i].rnum,s[i].name,s[i].marks);
}

15
Parameter Passing in a
Function
 Structure variables can be passed as parameters like
any other variables. Only the values will be copied
during function invocation

16
#include<stdio.h>typedef
struct
{
int x;int y;
}POINT;
void display(int, int);void
main()
{
POINT p1 = {2, 3};
display(p1.x, p1.y);
}
void display(int a, int b)
{
printf(" The coordinates of the point are: %d %d", a, b);
}

17
#include <stdio.h>typedef
struct
{
int x;int y;
}POINT;
void main()
{
POINT p1 = {2, 3};
display(p1);
}
void display(POINT p)
{
printf("The coordinates of the point are: %d %d", p.x, p.y);
}

19
#include<stdio.h>
#include<string.h>
struct student
{
int r_no;
char name[20];
char course[20];
float fees;
};
void main()
{
struct student stud1, *ptr_stud1;ptr_stud1 = &stud1;
ptr_stud1->r_no = 01;
strcpy(ptr_stud1->name, "Rahul");
strcpy(ptr_stud1->course, "BCA");
ptr_stud1->fees = 45000;
printf("n DETAILS OF STUDENT");
printf("n "); printf("n ROLL NUMBER = %d", ptr_stud1->r_no);
printf("n NAME = %s", ptr_stud1->name);
printf("n COURSE = %s", ptr_stud1->course);
printf("n FEES = %f", ptr_stud1->fees);
}

20
Defining data type: using typedef
 One may define a structure data-type with a single
name
typedef struct newtype {
member-variable1;
member-variable2;
.
member-variableN;
} mytype;
 mytype is the name of the new data-type
 Also called an alias for struct newtype
 Writing the tag name newtype is optional, can be
skipped
 Naming follows rules of variable naming

21
typedef : An example
typedef struct {
float real;
float imag;
} _COMPLEX;
 Defined a new data type named _COMPLEX. Now can
declare and use variables of this type
_COMPLEX a, b, c;

22
 Note: typedef is not restricted to just structures,
can define new types from any existing type
 Example:
 typedef int INTEGER
 Defines a new type named INTEGER from the
known type int
 Can now define variables of type INTEGER which
will have all properties of the int type
INTEGER a, b, c;

23
The earlier program using typedef
typedef struct{
float real;
float imag;
} _COMPLEX;
void swap (_COMPLEX a, _COMPLEX b)
{
_COMPLEX tmp;
tmp = a;
a = b;
b = tmp;
}

24
Contd.
void print (_COMPLEX a)
{
printf("(%f, %f) n",a.real,a.imag);
}
void main()
{
_COMPLEX x={4.0,5.0}, y={10.0,15.0};
print(x); print(y);
swap(x,y);
print(x); print(y);
}
swap.c

25
 Output:
(4.000000, 5.000000)
(10.000000, 15.000000)
(4.000000, 5.000000)
(10.000000, 15.000000)
 x and y are not swapped! But that has got
nothing to do with structures specially. We
will see its reason shortly

26
Exercise Problems
1. Extend the complex number program to include functions
for addition, subtraction, multiplication, and division
2. Define a structure for representing a point in two-
dimensional Cartesian co-ordinate system
• Write a function to compute the distance between two
given points
• Write a function to compute the middle point of the line
segment joining two given points
• Write a function to compute the area of a triangle, given
the co-ordinates of its three vertices

Introduction-to-structures-using-C-programming.ppt

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