Typedef

2 min read | C Tutorial

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Typing struct Student over and over gets old fast. typedef lets you create a nickname for a type — shorter, cleaner, and easier to read.

Basic typedef

With typedef, you define an alias. After that, you can use the alias just like any other type name.


#include <stdio.h>
typedef int Age;
int main() {
  Age myAge = 25;
  printf("I am %d years old\n", myAge);
  return 0;
}

typedef with Structs

This is where typedef really shines. Instead of struct Point p, you can just write Point p.


#include <stdio.h>
typedef struct {
  double real;
  double imag;
} Complex;
int main() {
  Complex c1 = {3.5, 2.1};
  Complex c2 = {1.0, 4.3};
  Complex sum;
  sum.real = c1.real + c2.real;
  sum.imag = c1.imag + c2.imag;
  printf("Sum: %.1f + %.1fi\n", sum.real, sum.imag);
  return 0;
}

typedef for Function Pointers

Function pointer syntax is ugly. typedef makes it readable by hiding the pointer mechanics behind a clean alias.


#include <stdio.h>
typedef int (*Operation)(int, int);
int add(int a, int b) { return a + b; }
int multiply(int a, int b) { return a * b; }
int main() {
  Operation op = add;
  printf("Result: %d\n", op(3, 4));
  op = multiply;
  printf("Result: %d\n", op(3, 4));
  return 0;
}