typedef in C

Introduction to typedef in C

typedef is a predefined keyword in C language. This typedef keyword tells the C compiler that “please assign a user given keyword to the already existing type”. It Means typedef gives an alternative user-friendly keyword for existing C language data types like unsigned int, long, int, char, float, etc. This concept is very useful when the existing data types a little bit handy to use then we will use this typedef concept.

Real-Time Example: Let’s take if we want to declare some variables like unsigned int then we have to write unsigned int always throughout the program is a very lengthy process. So, instead of that, we can assign a new name to the already existing data type then it is easy to use in the code. For this, we can use typedef keyword.

How does typedef Work in C Language?

This keyword works with typedef followed by existing data type and user wanted name to the data type. Then compiler will assume existing keyword name becomes user givenname for the entire application.

Syntax:

typedef<existing data type or keyword in C><user required name for the data type or keyword>;

Examples of typedef in C

Below given are the practical examples of typedef:

Example #1 – Typdef unsigned int ui;

Code: StructTypedef.c

#include <stdio.h>//Add all the basic C language libraries
#include <string.h>//Add the String library to perform string actions
//typedef for give struct keyword to user wanted keyword as like below (Courses)
typedef struct Courses {
char courseName[60];//declare character variable
float CourseFee;//declare float variable
char companyName[100];//declare character variable
int loginID;//declare integer variable
} Courses; //To make work user defined keyword we have call the keyword from here
//main method to execute application code
int main( ) {
//Taken Courses name as course( alias name)
Courses course;
//Copying character values into varaible
strcpy(course.courseName, "C Programming");
strcpy(course.companyName, "EDUCBA");
//Initailize float values into varaible
course.CourseFee = 5000.00;
//Initailize integer values into varaible
course.loginID=2452;
//display the output of all the declared variable below
printf( "Course Name : %s\n", course.courseName);
printf( "Company Name : %s\n", course.companyName);
printf( "Course Fee : %f\n", course.CourseFee);
printf( "Login ID : %d\n", course.loginID);
return 0;
}

Output:

Example #2 – Typedef union keyword

Code: TypedefUnion.c

#include <stdio.h>//Add all the basic C language libraries
#include <string.h>//Add the String library to perform string actions
//typedef for give struct keyword to user wanted keyword as like below (Employee)
typedef union Employee
{
inteID;//declare integer variable
float salary;//declare float variable
char company[30];//declare character variable
}Employee;//To make work user defined keyword we have call the keyword from here
//main method to execute application code
int main()
{
//Taken Courses name as course( alias name)
Employee e1, e2, e3, e4;
//Initailize float values into varaible
e1.salary = 18314912111343777091682304.000000 ;
//Initailize integer values into varaible
e1.eID=1769104726;
//Copying character values into varaible
strcpy(e1.company,"Verinon Technologies Private Limited");
//displaying employee details
printf("Details of First Employee\n");
printf("Employee ID : %d\n", e1.eID);
printf("Employee Salary : %f\n", e1.salary);
printf("Company Name : %s\n", e1.company);
//Initailize integer values into varaible
e2.eID = 1667330639 ;
//Initailize float values into varaible
e2.salary = 4158754218828133040128.000000;
//Copying character values into varaible
strcpy(e2.company,"Oracle Technologies Private Limited");
//displaying employee details
printf("Details of Second Employee\n");
printf("Employee ID : %d\n", e2.eID);
printf("Employee Salary : %f\n", e2.salary);
printf("Company Name : %s\n", e2.company);
//Initailize integer values into varaible
e3.eID = 1919117645;
//Initailize float values into varaible
e3.salary = 4504345476014339048099257778176.000000;
//Copying character values into varaible
strcpy(e3.company,"Microsoft Technologies Private Limited");
//displaying employee details
printf("Details of Third Employee\n");
printf("Employee ID : %d\n", e3.eID);
printf("Employee Salary : %f\n", e3.salary);
printf("Company Name : %s\n", e3.company);
//Initailize integer values into varaible
e4.eID = 1735356231 ;
//Initailize float values into varaible
e4.salary = 1130698294087203659186176.000000;
//Copying character values into varaible
strcpy(e4.company,"Google Technologies Private Limited");
//displaying employee details
printf("Details of Fourth Employee\n");
printf("Employee ID : %d\n", e4.eID);
printf("Employee Salary : %f\n", e4.salary);
printf("Company Name : %s\n", e4.company);
return 0;
}
course.loginID=2452;
//display the output of all the declared variable below
printf( "Course Name : %s\n", course.courseName);
printf( "Company Name : %s\n", course.companyName);
printf( "Course Fee : %f\n", course.CourseFee);
printf( "Login ID : %d\n", course.loginID);
return 0;
}

Output:

Example #3 – Typedef unsigned char

Code: TypedefUnsignedChar.c

#include <stdio.h>//Add all the basic C language libraries
int main()
{
//typedef for give struct keyword to user wanted keyword as like below
typedef unsigned char uchar;
//declare character variable with user defined keyword
uchar alphabet = 'a';
//declare character variable with user defined keyword
uchar a='P';
//declare character variable with user defined keyword
uchar b='b';
//declare character variable with user defined keyword
uchar c = 'C';
//declare character variable with user defined keyword
uchar d='d';
//declare character variable with user defined keyword
uchar e = 'E';
//declare character variable with user defined keyword
uchar f='f';
//declare character variable with user defined keyword
uchar g='g';
//Displaying output of the user
printf("alphabet inside main() : %c\n", alphabet);
printf("alphabet inside main() : %c\n", a);
printf("alphabet inside main() : %c\n", b);
printf("alphabet inside main() : %c\n", c);
printf("alphabet inside main() : %c\n", d);
printf("alphabet inside main() : %c\n", e);
printf("alphabet inside main() : %c\n", f);
printf("alphabet inside main() : %c\n", g);
return 0;
}

Output:

Conclusion

Typedef is used to declare predefined C data types or keywordswith user defined names. It reduces the repetition same data type again and again. We can conclude by this we can change any c data type name with any user wanted name.

Recommended Articles

This is a guide to typedef in C. Here we also discuss the Introduction and how does typedef work along with examples and its code implementation. You may also have a look at the following articles to learn more –

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