C Programming Structure
Structure is the collection of variables of different types under a
single name for better handling. For example: You want to store the information
about person about his/her name, citizenship number and salary. You can create
these information separately but, better approach will be collection of these
information under single name because all these information are related to
person.
Structure Definition in C
Keyword
struct is used for creating a structure.
Syntax of structure
struct structure_name
{
data_type member1;
data_type member2;
.
.
data_type memeber;
};
We can create the structure for a person as mentioned above as:
struct person
{
char name[50];
int cit_no;
float salary;
};
This declaration above creates the derived data type
struct person.
Structure variable declaration
When a structure is defined, it creates a user-defined type but, no
storage is allocated. For the above structure of person, variable can be
declared as:
struct person
{
char name[50];
int cit_no;
float salary;
};
Inside main function:
struct person p1, p2, p[20];
Another way of creating sturcture variable is:
struct person
{
char name[50];
int cit_no;
float salary;
}p1 ,p2 ,p[20];
In both cases, 2 variables p1, p2 and array p
having 20 elements of type struct person are created.
Accessing members of a structure
There are two types of operators used for accessing members of a
structure.
- Member operator(.)
- Structure pointer operator(->) (will be discussed in structure and pointers chapter)
Any member of a structure can be accessed as:
structure_variable_name.member_name
Suppose, we want to access salary for variable p2. Then,
it can be accessed as:
p2.salary
Example of structure
Write a C
program to add two distances entered by user. Measurement of distance should be
in inch and feet.(Note: 12 inches = 1 foot)
#include <stdio.h>
struct Distance{
int feet;
float inch;
}d1,d2,sum;
int main(){
printf("1st distance\n");
printf("Enter feet: ");
scanf("%d",&d1.feet); /* input of feet for structure variable d1 */
printf("Enter inch: ");
scanf("%f",&d1.inch); /* input of inch for structure variable d1 */
printf("2nd distance\n");
printf("Enter feet: ");
scanf("%d",&d2.feet); /* input of feet for structure variable d2 */
printf("Enter inch: ");
scanf("%f",&d2.inch); /* input of inch for structure variable d2 */
sum.feet=d1.feet+d2.feet;
sum.inch=d1.inch+d2.inch;
if (sum.inch>12){ //If inch is greater than 12, changing it to feet.
++sum.feet;
sum.inch=sum.inch-12;
}
printf("Sum of distances=%d\'-%.1f\"",sum.feet,sum.inch);
/* printing sum of distance d1 and d2 */
return 0;
}
Output
1st distance
Enter feet: 12
Enter inch: 7.9
2nd distance
Enter feet: 2
Enter inch: 9.8
Sum of distances= 15'-5.7"
Structures within structures
Structures can be nested within other structures in C programming.
struct complex
{
int imag_value;
float real_value;
};
struct number{
struct complex c1;
int real;
}n1,n2;
C Programming Structure and Pointer
Pointers can be accessed along with structures. A pointer variable
of structure can be created as below:
struct name {
member1;
member2;
.
.
};
-------- Inside function -------
struct name *ptr;
Here, the pointer variable of type struct name is created.
Structure's member through pointer can be used in two ways:
- Referencing pointer to another address to access memory
- Using dynamic memory allocation
Consider an example to access structure's member through pointer.
#include <stdio.h>
struct name{
int a;
float b;
};
int main(){
struct name *ptr,p;
ptr=&p; /* Referencing pointer to memory address of p */
printf("Enter integer: ");
scanf("%d",&(*ptr).a);
printf("Enter number: ");
scanf("%f",&(*ptr).b);
printf("Displaying: ");
printf("%d%f",(*ptr).a,(*ptr).b);
return 0;
}
In this example, the pointer variable of type
struct name is referenced to the address of p. Then, only the
structure member through pointer can can accessed.
Structure pointer member can also be accessed using
->
operator.(*ptr).a is same as ptr->a
(*ptr).b is same as ptr->b
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