Structures
Why uses
structure?
we need to keep more than one attribute for an entity in program. It is
capable of having various properties from various data types.
As for example students may have a name (string),
roll number (int), and marks (float). let we have to store some properties related to a Student
like a Name, Class, and div etc. We have one method to create a character array
to store the Name, integer variable for Class, and character variable for div.
The structure is a user-defined data structure that is used to bind two
or more data types or data structures together.
For storing the details of a student, we can create a structure for a
student that has the following data types-
a character array for storing
name,
an integer for storing roll
number, and
a character for storing div, etc.
Structures don't take up any space in the memory unless and until we
define some variables for it. When we define its variables, they take up some
memory space which depends upon the type of the data member .
Defining a Structure
To define a structure,
use the struct keyword statement.
Syntax-:
struct name_of_the_structure
{
data_type member1;
data_type member2;
...
data_type memberN;
}; varibles;
Eg.
struct Store
{
// structure definition
char storeName
int totalBooks;
char storeLicense[20];
} storeA, storeB; // structure
variables
How to Declare
structure variable?
To make it simple to access a structure member, we can create a variable
for the structure. Structure variables can be declared in one of two ways:
1. By using the struct keyword in the main () method.
2. By declaring a variable when the structure is defined.
Eg.
struct employee
{
int id;
char name[50];
float salary;
}e1,e2;
Initialize Structure Members
Eg.
struct Student student1 = {"Student_name"
, 1, 'A'};
Accessing members of the structure
There are two ways to access structure
members:
1. By . (member or dot operator)
2. By -> (structure pointer operator)
Structure members can be accessed and
assigned values in a number of ways. Structure members have no meaning
individually without the structure. the
member name must be linked with the structure variable using a
dot . operator also called period or member
access operator.
Example 1
{
char name[25];
int age;
char branch[10];
char gender;
}S1, S2;
Example2
#include<stdio.h>
#include<string.h>
struct Student
{
char name[25];
int age;
char branch[10];
char gender;
};
{
struct Student s1;
/*
s1 is a variable of Student type and
age is a member of Student
*/
s1.age = 18;
/*
using string function to add name
*/
strcpy(s1.name, "Viraaj");
/*
displaying the stored values
*/
printf("Name of Student 1: %s\n", s1.name);
printf("Age of Student 1: %d\n", s1.age);
return 0;
}
Nested Structure
The nested word means placed or stored
one inside the other. As the structure in C is a user-defined data type so
while creating a structure, we can define another structure as its data member,
which leads to a structure with another structure inside it.
#include <stdio.h>
struct Student
{
char name[50];
int class;
// defining a nested structure
struct Address
{
char city[50];
int pincode;
}addr;
} student = {"Student_one", 5,
"city_1", 1234};
// variable defined with structure
struct Subject
{
char name[50];
char book[50];
};
struct Teacher
{
char name[50];
// added already defined structure
struct Subject subject;
};
{
// declaring variable for Teacher structure
struct Teacher teacher;
scanf("%s",teacher.name);
scanf("%s",teacher.subject.name);
scanf("%s",teacher.subject.book);
// printing values for teacher variable
printf("Name : %s\:
%s\n",teacher.name,teacher.sub);
// printing values for student variable
printf("Name : %s\n City: %s",student.name,student.city);
return 0;
}
We can also declare an array of structure variables.
in which each element of the array will represent a structure variable.
Example : struct
employee emp[5];
{
char ename[10];
int sal;
};
struct Employee emp[5];
int i, j;
void ask()
{
for(i = 0; i < 3; i++)
{
printf("\nEnter %dst Employee record:\n", i+1);
printf("\nEmployee name:\t");
scanf("%s", emp[i].ename);
printf("\nEnter Salary:\t");
scanf("%d", &emp[i].sal);
}
printf("\nDisplaying Employee record:\n");
for(i = 0; i < 3; i++)
{
printf("\nEmployee name is %s", emp[i].ename);
printf("\nSlary is %d", emp[i].sal);
}
}
void main()
{
ask();
}
Passing Structures
to Function
We can pass a structure as a function argument just
like we pass any other variable or an array as a function argument.
You can pass a structure as a function
argument in the same way as you pass any other variable or pointer.
#include<stdio.h>
{
char name[10];
int roll;
};
{
struct Student std;
printf("\nEnter Student record:\n");
printf("\nStudent name:\t");
scanf("%s", std.name);
printf("\nEnter Student rollno.:\t");
scanf("%d", &std.roll);
show(std);
}
{
printf("\nstudent name is %s", st.name);
printf("\nroll is %d", st.roll);
}
A pointer is a variable that stores the address of another variable. As
a structure consists of some data types or data structures for which memory is
allocated to the structure variable, we can use a structure pointer to store
the address of that memory. A structure pointer is essentially a pointer to a
structure variable.
use the arrow operator (->) to
access the structure member using a pointer.
Example
The following example illustrates the
pointer to a structure .
#include<stdio.h>
struct myStruct
{
int x, y;
};
int main()
{
struct myStruct var1 =
{1, 2};
// var2 is a pointer to
structure var1.
struct myStruct *var2 =
&var1;
// Accessing data
members of myStruct using a structure pointer.
printf("%d
%d", var2->x, var2->y);
return 0;
}
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