Pointers to Structures

In C language, you can use pointers to structures to access and manipulate the members of a structure dynamically, and to pass structures as arguments to functions. Here’s an example:

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

struct student {
    char name[50];
    int age;
    float gpa;
};

void print_student(struct student *s) {
    printf("Name: %s\n", s->name);
    printf("Age: %d\n", s->age);
    printf("GPA: %.2f\n", s->gpa);
}

int main() {
    // Declare a student structure and initialize it
    struct student john;
    strcpy(john.name, "John Smith");
    john.age = 19;
    john.gpa = 3.2;

    // Declare a pointer to a student structure and assign the address of john to it
    struct student *john_ptr = &john;

    // Print out the information for john using the print_student function
    printf("Information for john:\n");
    print_student(john_ptr);

    // Dynamically allocate memory for a new student structure and set its values
    struct student *jane_ptr = malloc(sizeof(struct student));
    strcpy(jane_ptr->name, "Jane Doe");
    jane_ptr->age = 20;
    jane_ptr->gpa = 3.8;

    // Print out the information for jane using the print_student function
    printf("Information for jane:\n");
    print_student(jane_ptr);

    // Free the dynamically allocated memory for jane
    free(jane_ptr);

    return 0;
}

In this example, we first define a struct called student, which contains three members: a character array for the student’s name, an integer for their age, and a floating-point number for their GPA.

We then declare a print_student function that takes a pointer to a student structure as its argument and prints out the information for that student using the arrow operator -> to access the structure members.

In main, we first declare a student structure called john and initialize its values. We then declare a pointer to a student structure called john_ptr and assign the address of john to it using the address-of operator &.

We call the print_student function to print out the information for john using john_ptr.

We then dynamically allocate memory for a new student structure called jane_ptr using the malloc function. We set the values for jane_ptr using the arrow operator ->. We then call print_student to print out the information for jane_ptr.

Finally, we free the dynamically allocated memory for jane_ptr using the free function.