Structs and pointers

Learn struct pointers and the -> operator.

Structs and pointers

Holding a pointer to a struct is the basic way to pass large data without copying. First you define struct Person { char name[32]; int age; }. Then you create a variable with struct Person p1; and a pointer with struct Person *ptr = &p1;.

To access a field through the pointer you use the arrow operator ->: ptr->age = 30;. This is shorthand for (*ptr).age. Parentheses are required; *ptr.age is parsed wrong. The arrow is both shorter and clearer about intent; that's why it's common in C code.

-> and (*ptr).field are equivalent

The arrow operator -> is essentially the combination of * indirection and . access. That is, ptr->age and (*ptr).age are the same.

Example: you define struct Person p1 = {"Ayşe", 25}; and struct Person *ptr = &p1;. Both ptr->age and (*ptr).age give 25. Without parentheses *ptr.age parses as *(ptr.age); this is a compile error or undefined behavior. Modern C prefers the arrow; it's more readable.

Exercise Assign a field via pointer and print

Define struct Person with char name[32]; and int age;. In main, write struct Person p1; and struct Person *ptr = &p1;. Assign with ptr->age = 30; and print with printf("%d\n", ptr->age);.

Show example solution

#include <stdio.h>

struct Person {
    char name[32];
    int age;
};

int main(void) {
    struct Person p1;
    struct Person *ptr = &p1;
    ptr->age = 30;
    printf("%d\n", ptr->age);
    return 0;
}

Test yourself

How do you access age through the ptr pointer?
- &ptr.age
- ptr.age
- *ptr.age
- ptr->age
Show answer

ptr->age — The -> operator accesses a field through a pointer.

Assign a field through a pointer

struct Person p1;
struct Person *ptr = &p1;
ptr____ = 30;
printf("%d\n", ptr->age);

Show answer

struct Person p1;
struct Person *ptr = &p1;
ptr->age = 30;
printf("%d\n", ptr->age);

Match the access forms

ptr->age

Pointer access
(*ptr).age

Indirect access
p1.age

Value access
&p1

Address-of

Next lesson: Dynamic struct

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