C structs and Pointers (With Examples) (2024)

Before you learn about how pointers can be used with structs, be sure to check these tutorials:

C Pointers to struct

Here's how you can create pointers to structs.

struct name { member1; member2; . .};int main(){ struct name *ptr, Harry;}

Here, ptr is a pointer to struct.

Example: Access members using Pointer

To access members of a structure using pointers, we use the -> operator.

#include <stdio.h>struct person{ int age; float weight;};int main(){ struct person *personPtr, person1; personPtr = &person1; printf("Enter age: "); scanf("%d", &personPtr->age); printf("Enter weight: "); scanf("%f", &personPtr->weight); printf("Displaying:\n"); printf("Age: %d\n", personPtr->age); printf("weight: %f", personPtr->weight); return 0;}

In this example, the address of person1 is stored in the personPtr pointer using personPtr = &person1;.

Now, you can access the members of person1 using the personPtr pointer.

Dynamic memory allocation of structs

Before you proceed this section, we recommend you to check C dynamic memory allocation.

Sometimes, the number of struct variables you declared may be insufficient. You may need to allocate memory during run-time. Here's how you can achieve this in C programming.

Example: Dynamic memory allocation of structs

#include <stdio.h>#include <stdlib.h>struct person { int age; float weight; char name[30];};int main(){ struct person *ptr; int i, n; printf("Enter the number of persons: "); scanf("%d", &n); // allocating memory for n numbers of struct person ptr = (struct person*) malloc(n * sizeof(struct person)); for(i = 0; i < n; ++i) { printf("Enter first name and age respectively: "); // To access members of 1st struct person, // ptr->name and ptr->age is used // To access members of 2nd struct person, // (ptr+1)->name and (ptr+1)->age is used scanf("%s %d", (ptr+i)->name, &(ptr+i)->age); } printf("Displaying Information:\n"); for(i = 0; i < n; ++i) printf("Name: %s\tAge: %d\n", (ptr+i)->name, (ptr+i)->age); return 0;}

When you run the program, the output will be:

Enter the number of persons: 2Enter first name and age respectively: Harry 24Enter first name and age respectively: Gary 32Displaying Information:Name: HarryAge: 24Name: GaryAge: 32

In the above example, n number of struct variables are created where n is entered by the user.

To allocate the memory for n number of struct person, we used,

ptr = (struct person*) malloc(n * sizeof(struct person));

Then, we used the ptr pointer to access elements of person.