Structure Pointer in C

You can use structure pointers to work with structures (structs) more efficiently and flexibly. Structure pointers allow you to manipulate the members of a structure using pointers, which can be particularly useful when working with dynamic memory allocation and data structures.

Here’s how you can declare, create, and use structure pointers in C:

1. Defining a Structure: First, you define a structure that represents the data you want to work with. For example:

 struct Student {
     char name[50];
     int roll_number;
     float GPA;
 };

2. Declaring a Structure Pointer: You can declare a pointer to a structure using the structure’s name followed by an asterisk (*). For example:

 struct Student *studentPtr;

3. Allocating Memory Dynamically: To allocate memory for a structure dynamically (usually on the heap), you can use functions like malloc or calloc. For example:

 studentPtr = (struct Student *)malloc(sizeof(struct Student));

This allocates memory for a single struct Student and assigns the pointer studentPtr to the allocated memory.

4. Accessing Structure Members using Pointers: You can access the members of the structure using the -> operator with the structure pointer. For example:

 strcpy(studentPtr->name, "John");
 studentPtr->roll_number = 101;
 studentPtr->GPA = 3.75;

This code sets the values of the structure members using the pointer studentPtr.

5. Deallocating Memory: Don’t forget to deallocate the memory when you’re done with it to prevent memory leaks. You can use the free function:

 free(studentPtr);

Here’s a complete example that demonstrates the usage of structure pointers:

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

struct Student {
    char name[50];
    int roll_number;
    float GPA;
};

int main() {
    struct Student *studentPtr;

    // Allocate memory for a student
    studentPtr = (struct Student *)malloc(sizeof(struct Student));

    // Check if memory allocation was successful
    if (studentPtr == NULL) {
        printf("Memory allocation failed.\n");
        return 1;
    }

    // Initialize the structure members
    strcpy(studentPtr->name, "John");
    studentPtr->roll_number = 101;
    studentPtr->GPA = 3.75;

    // Access and print the structure members
    printf("Name: %s\n", studentPtr->name);
    printf("Roll Number: %d\n", studentPtr->roll_number);
    printf("GPA: %.2f\n", studentPtr->GPA);

    // Deallocate the memory
    free(studentPtr);

    return 0;
}

This example demonstrates the use of a structure pointer to allocate memory dynamically for a struct Student, initialize its members, access and print those members, and finally, deallocate the memory to avoid memory leaks.