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 a_lex.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
