c / c-fundamentals
20 mins
C Level 7: Structs, Typedef & Pointer Access (->)
Why This Matters: Structs allow programmers to define complex custom data models grouping related heterogeneous fields.
## Structures & The Arrow Operator
A `struct` groups related variables under a single custom record type.
```c
typedef struct {
int id;
char name[50];
float gpa;
} Student;
Student s1 = {101, "Alice", 3.95};
// Access via pointer using arrow operator (->)
Student *ptr = &s1;
printf("ID: %d
", ptr->id); // Equivalent to (*ptr).id
```
MENTAL MODEL & MEMORY LAYOUT
STRUCT IN MEMORY:
Student s1 (0x3000):
[ id (4B) ][ name (50B) ][ gpa (4B) ]
▲
│ Arrow Operator (ptr->id)
ptr (0x3000) COMMON PITFALLS TO AVOID
- Using dot operator `.` on struct pointers instead of arrow operator `->`.
- Forgetting semicolon `;` at end of struct definition.
Struct Pointer Selection
#include <stdio.h>
typedef struct {
int x;
int y;
} Point;
void move(Point *p, int dx, int dy) {
p->x += dx;
p->y += dy;
}
int main() {
Point pt = {10, 20};
move(&pt, 5, 5);
printf("Point: (%d, %d)\n", pt.x, pt.y);
return 0;
}Mutates struct fields inside function using struct pointer arrow operator `->`.
CONCEPT MASTERY CHECKPOINT
When accessing a struct field through a pointer `Student *ptr`, which operator is used?
NEXT RECOMMENDED LESSON
C Level 8: File Handling & Streams
Challenge: Define a struct `Rectangle` with width and height, and print the calculated area.