C structs and Pointers

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

• C Pointers
• C struct

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.

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.

By the way,

• personPtr->age is equivalent to (*personPtr).age
• personPtr->weight is equivalent to (*personPtr).weight

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

When you run the program, the output will be:

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