Structure in C by declaring variables and displaying elements of struct array

By using arrays we can store items of single data type. Student id ( roll number ) , name , mark ,class are different data types but they belong to same entity student. Here we can declare a structure to store all details of the student which consist of different data types.

Declaring structure variables.

int main()
{
struct Students{
	int id;
	char name[50];
	float mark[5];
	}; 
struct Students s1,s2;
struct Students s3={5,"Ronn",12.5};	

return 0;
}

Here s1,s2,s3 are variables of type struct Students.
Students is the tagname. We used this tagname to create struct Variables.

Structure is declared to create an template only, we can't initialize the structure at the time of declaring it.
This is not allowed.

struct Students{
	int id=1;  // Not valid 
	char name[50]="Ravi"; // Not valid
	float mark[5]=4.5; // Not valid 
	};

Assigning data to struct variables

We can read user input and assing the data to struct variables.

int main()
{
struct Students{
	int id;
	char name[50];
	float mark;
	}; 
struct Students s1,s2;
printf("\nEnter ID :");
scanf("%d",&s2.id);
printf("\nEnter name :");
scanf("%s",&s2.name);
printf("\nEnter mark :");
scanf("%f",&s2.mark);
// Input over now display data ///
printf("\n\n ID:  %d",s2.id);
printf("\n name:  %s",s2.name);
printf("\n mark:  %f",s2.mark);

return 0;
}

Array of structure

Using array we store user entered data and display the same. Similarly we can create array of structure for struct variables.

int main()
{
struct Students{
	int id;
	char name[50];
	float mark;
	}std[2]; 
int i;
for(i=0;i<2;i++){
printf("\nEnter ID :");
scanf("%d",&std[i].id);
printf("\nEnter name :");
scanf("%s",&std[i].name);
printf("\nEnter mark :");
scanf("%f",&std[i].mark);
}
// Input is over , now display ///
for(i=0;i<2;i++){
printf("\n\n ID:  %d",std[i].id);
printf("\n name:  %s",std[i].name);
printf("\n mark:  %f",std[i].mark);
}
return 0;
}

We can directly assign data to struct variable ( without any user input )

int main()
{
struct Students{
	int id;
	char name[50];
	float mark;
	}; 
int i;
struct Students std[2]={
	{1,"Ronn",5.6},
	{2,"Geek",7.3}
};

// Input is over , now display ///

for(i=0;i<2;i++){
printf("\n\n ID:  %d",std[i].id);
printf("\n name:  %s",std[i].name);
printf("\n mark:  %f",std[i].mark);
}
return 0;
}

Output

 ID:  1
 name:  Ronn
 mark:  5.600000

 ID:  2
 name:  Geek
 mark:  7.300000

Accessing the value of structure variable.

We can use dot (.) operators to access the value of structure variables.

printf("Name:  %s",s3.name); // Ronn

Copying data of elements

We used strcpy() to copy string data.

int main()
{
struct Students{
	int id;
	char name[50];
	float mark;
	}; 
int i;
struct Students s1;
struct Students s2={5,"Ronn",12.5};
/// copying data from s2 to s1 ///
s1.id=s2.id+1;
strcpy(s1.name,s2.name);
s1.mark=s2.mark-0.1;

printf("ID : %d",s1.id);
printf("\nName : %s",s1.name);
printf("\nMark : %f",s1.mark);
return 0;
}

Output is here

ID : 6
Name : Ronn
Mark : 12.400000

Example: Nested Structures

Nested Structures: Demonstrates how to manage more complex data with structures inside structures.

#include <stdio.h>

struct address {
    char city[30];
    int pin;
};

struct employee {
    char name[50];
    struct address emp_address;
    int salary;
};

int main() {
    struct employee emp = {"John Doe", {"New York", 10001}, 50000};
    printf("Employee: %s, City: %s, Pin: %d\n", emp.name, emp.emp_address.city, emp.emp_address.pin);
    return 0;
}

Example: Using Pointers to Structures

Structure Pointers: Improves performance by accessing structure members through pointers.

#include <stdio.h>

struct employee {
    char name[50];
    int salary;
};

int main() {
    struct employee emp = {"John Doe", 50000};
    struct employee *ptr = &emp;
    printf("Employee: %s, Salary: %d\n", ptr->name, ptr->salary);
    return 0;
}

Structure elements are stored in contiguous memory locations. So directly we can copy one element to other.
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