C programming structure explanation with example

Structure in C, explanation with example :

The structure is a user-defined data type in C. For example, suppose we want to store numbers from 1 to 100. We will use one integer array of size 100. But if we need to store the details of 100 students, each detail will include name, age, and marks for a specific subject, what we will do? To solve such problems, we can use Structure.

Creating a simple structure :

struct Student{
	char name[20];
	int age;
	int marks;
};

It will create one structure Student. It will create one user-defined data type, but it will not allocate any memory. For that, we need to create variables of this data type.

Declaring variables :

We can declare variables of type Student as below :

#include<stdio.h>

struct Student{
	char name[20];
	int age;
	int marks;
};

int main(){
	struct Student class10[10];
	struct Student alex,bryan,chandler;
}

– In the above example, we have created one array class10 of type Student and size 10. Means, it has 10 elements and each element is of type Student.
– We have also created few other Student variables alex, bryan, and chandler.

We can also declare all variables while defining the structure type like below :

#include<stdio.h>

struct Student{
	char name[20];
	int age;
	int marks;
}class10[10],alex,bryan,chandler;

int main(){
	
}

Using ‘typedef’ in structure :

In the above example, we use the struct keyword while declaring a variable like :

struct Student class10[10];
struct Student alex,bryan,chandler;

We can use typedef keyword to omit the repeated use of struct keyword like below :

typedef struct {
	char name[20];
	int age;
	int marks;
}Student;

int main(){
	 Student class10[10];
	 Student alex,bryan,chandler;
}

The code looks much cleaner now. Isn’t it?

Accessing values of a structure variable :

We can use one dot (‘.’) to access all items lies inside a structure variable. For example, if we want to access the name of a Student ‘alex’, we can use alex.name. Similarly, to set a value we can use same a dot in the same way. Let’s try it with an example :

#include<stdio.h>
#include<string.h>

typedef struct {
	char name[20];
	int age;
	int marks;
}Student;

int main(){
	 Student chandler;

	 strcpy(chandler.name,"Chandler Bing");
	 chandler.age = 20;
	 chandler.marks = 87;

	 printf("Name : %s\n",chandler.name);
	 printf("Age : %d\n",chandler.age);
	 printf("Marks : %d\n",chandler.marks);
}

It will print the below output :

Name : Chandler Bing
Age : 20
Marks : 87

So, basically, we are assigning values to the variable and then retrieving them again.

Passing structure variable to a function :

We can pass a structure variable to a different function in the same way we pass other variables to a function. Let’s explore this with an example :

#include<stdio.h>
#include<string.h>

typedef struct {
	char name[20];
	int age;
	int marks;
}Student;

void printAllName(Student students[],int count){
	int i;

	for(i=0; i<count; i++){
		printf("Name : %s , Age : %d , Marks : %d\n",students[i].name,students[i].age,students[i].marks);
	}
}

int main(){
	 Student class10[3];

	 strcpy(class10[0].name,"Chandler");
	 class10[0].age = 20;
	 class10[0].marks = 87;

	 strcpy(class10[1].name,"Edward");
	 class10[1].age = 22;
	 class10[1].marks = 77;

	 strcpy(class10[2].name,"Frank");
	 class10[2].age = 19;
	 class10[2].marks = 57;

	 printAllName(class10,3);
}

It will print out :

Name : Chandler , Age : 20 , Marks : 87
Name : Edward , Age : 22 , Marks : 77
Name : Frank , Age : 19 , Marks : 57

Using a pointer to store the address of a Structure :

We can store the address of a Structure variable in any other variable. To access any element of the Structure, we will have to use ‘->’ symbol. Let me show you with an example :

#include<stdio.h>
#include<string.h>

typedef struct {
	char name[20];
	int age;
	int marks;
}Student;

int main(){
	 Student student;
	 Student* address_pointer;

	 strcpy(student.name,"Chandler");
	 student.age = 20;
	 student.marks = 87;
	 address_pointer = &student;

	 printf("Name : %s\n",address_pointer->name);
	 printf("Marks : %d\n",address_pointer->marks);
	 printf("Age : %d\n",address_pointer->age);
}

Output :

Name : Chandler
Marks : 87
Age : 20

Leave a Reply