Typedef in C with examples

Consider following example:

#include<stdio.h>

   struct student{

       int rollno;

       float marks;

   };

int main(){

   struct student s1;

   s1.rollno=12;

   s1.marks=92.5;

  

   printf("\nStudent 1 Details\n");

   printf("\nRoll No:%d",s1.rollno);

   printf("\nMarks:%.2f\n",s1.marks);

  

   struct student s2;

   s2.rollno=13;

   s2.marks=90;

  

   printf("\nStudent 2 Details\n");

   printf("\nRoll No:%d",s2.rollno);

   printf("\nMarks:%.2f\n",s2.marks);

 return 0;

}

As you can see in above example, every time, a structure variable is being declared, we have to write struct student varName.

To avoid writing struct all over the place, we can use typedef with structure declaration. Using a typedef avoids having to write struct every time you declare a variable of that type.

 Example:

#include<stdio.h>

   typedef struct student{

       int rollno;

       float marks;

   };

int main(){

   student s1;

   s1.rollno=12;

   s1.marks=92.5;

  

   printf("\nStudent 1 Details\n");

   printf("\nRoll No:%d",s1.rollno);

   printf("\nMarks:%.2f\n",s1.marks);

  

   student s2;

   s2.rollno=13;

   s2.marks=90;

  

   printf("\nStudent 2 Details\n");

   printf("\nRoll No:%d",s2.rollno);

   printf("\nMarks:%.2f\n",s2.marks);

 return 0;

}

Another version of above program:

  #include<stdio.h>

   typedef struct {

       int rollno;

       float marks;

   }student;

int main(){

   student s1;

   s1.rollno=12;

   s1.marks=92.5;

  

   printf("\nStudent 1 Details\n");

   printf("\nRoll No:%d",s1.rollno);

   printf("\nMarks:%.2f\n",s1.marks);

  

   student s2;

   s2.rollno=13;

   s2.marks=90;

  

   printf("\nStudent 2 Details\n");

   printf("\nRoll No:%d",s2.rollno);

   printf("\nMarks:%.2f\n",s2.marks);

 return 0;

}

Another version of same program:

  #include<stdio.h>

   struct student{

       int rollno;

       float marks;

   };

   typedef struct student;

int main(){

   student s1;

   s1.rollno=12;

   s1.marks=92.5;

  

   printf("\nStudent 1 Details\n");

   printf("\nRoll No:%d",s1.rollno);

   printf("\nMarks:%.2f\n",s1.marks);

  

   student s2;

   s2.rollno=13;

   s2.marks=90;

  

   printf("\nStudent 2 Details\n");

   printf("\nRoll No:%d",s2.rollno);

   printf("\nMarks:%.2f\n",s2.marks);

 return 0;

}

Another version of above program:

  #include<stdio.h>

   struct student{

       int rollno;

       float marks;

   };

   typedef struct student s;

int main(){

   s s1;

   s1.rollno=12;

   s1.marks=92.5;

  

   printf("\nStudent 1 Details\n");

   printf("\nRoll No:%d",s1.rollno);

   printf("\nMarks:%.2f\n",s1.marks);

  

   s s2;

   s2.rollno=13;

   s2.marks=90;

  

   printf("\nStudent 2 Details\n");

   printf("\nRoll No:%d",s2.rollno);

   printf("\nMarks:%.2f\n",s2.marks);

 return 0;

}

Summary:

(i). Typedef keyword is used to give a new symbolic name(i.e alias) to another existing type.

(ii). It saves some typing.

(iii). It makes code cleaner.

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