Typedef Struct in C++

The C++ programming language offers a “typedef” keyword which allows the developers to create aliases of existing data types which can be basic primitive types like “int”, “long”, or user-defined structure data types. The “typedef” keyword does not create a new type. Instead, it creates a nickname (or an alias) of an existing type. The use of “typedef” can make the code more readable and save the energy and time needed to type out long type names repeatedly. However, if it is used too much in the program, it might make the code confusing, especially in big projects. In this article, we will explore how to define a structure with “typedef”, how it helps to reduce the code line, what the usage of “typedef” is, and much more with the help of illustrative examples.

Understanding the Typedef Struct in C++

In C++, “typedef” is a keyword that provides new names of existing built-in data types, pointers, structures, and user-defined data types that work as an alias in the whole program. To simply put it, it gives descriptive names to the built-in or user-defined data types which can be self-explanatory. It also helps reduce the lines of code and simplify the complicated data types. However, as mentioned earlier, too much use of “typedef” is not recommended because it can lead to confusion.

The struct is another keyword that is used to define and initialize a structure. The structure in C++ is a composite data type declaration that allows the developers to group various data types or variables in one place.

In C++, “struct” and “typedef struct” are the same. There is no practical difference between “typedef struct” and “struct” as they work the same. Whenever a class, enum, union, or struct is declared or defined in C++, it is unnecessary to implicitly define them as “typedef” because they are, by default, “typedef”.

Syntax of the Typedef Struct in C++

The syntax of the “typedef” struct is the same as the struct with no “typedef”. It just needs an explicit definition of “typedef” with the “struct” keyword. See the complete syntax in the following:

typedef struct {
<data_type> <variable1>;
<data_type> <variable2>;
<data_type> <variable3>;
}<struct_name> ;

The structure is defined now by simply using the <struct_name>. We can define multiple variables of this structure type. See the following definition:

<struct_name> variable4, variable5, variable6;

Now, let us explore some examples for a clearer and better understanding of the “typedef” struct in C++.

Example 1:

In the first example of the “typedef” struct in C++, we take a simple program to explain how it can be defined and used in C++ projects. See the following code and then let us move on to the explanation:

using namespace std;
struct decimal{
  int dec1;
  int dec2; };
int main() {
    struct decimal d;
    d.dec1 = 10;
    d.dec2 = 23;
    return 0;}

In this C++ code, we define a decimal structure and demonstrate its usage within the main function. Let's take a look at each line of code.

The program starts with including the necessary header file like “#include<iostream>” and using the “std” namespace for input/output operations and bring the “std” namespace into scope. After that, a structure named “decimal” is defined. The structure has two members: “dec1” and “dec2”, both of type “int”.

In the main function, an instance of the decimal structure is created. This is done using the “d;” declaration decimal. The structure has two members, so we access both using the “d” instance. The values of “dec1” and “dec2” are then assigned with 10 and 23, respectively, using the “d.dec1” and “d.dec2” definition. Finally, the values of “dec1” and “dec2” are printed to the console using “cout”. The program gives the following outputs:

The given output snapshot shows how a simple “typedef” structure named “decimal” is used to store and manipulate two decimal numbers within the main function. The “typedef” struct allows for better organization and management of related data in a C++ program.

Example 2:

In the example that we previously explained, only one type of data is given in the structure. Now, let us define multiple types of data in a structure and see how “typedef” can help in reducing the line of codes and simplifying the complications of the code. The code is given in the following for your reference:

using namespace std;
typedef struct dictionary {
int id;
string name;
long rollnum;
char classname;
int main()
dict data;
data.id = 20;
data.name = "Kalsoom";
data.rollnum = 123456789;
data.classname = 'D';
cout <<"The id of the candidate is = " <<data.id<<endl;
cout <<"The name of the candidate is = " <<data.name<<endl;
cout <<"The rollnum of the candidate is = " <<data.rollnum<<endl;
cout <<"The class name of the candidate is = " <<data.classname<<endl;
return 0;

Like the previous example, this program has also started the necessary header file like “#include<iostream>” and using the “std” namespace to perform the basic input/output operations. After that, a dictionary structure is defined with four members: id, name, rollnum, and classname. The “typedef” keyword creates a “dict” alias for this structure. This alias allows the structure to be referred to simply as “dict” instead of the struct dictionary.

Now, in the main function, we first define an instance of the structure dictionary named “dict” as a data that acts as an alias of “dict”. The values are assigned to each member of the structure using the following statements:

    data.id = 20;
    data.name = "Kalsoom";
    data.rollnum = 123456789;
    data.classname = 'D';

As you can observe, these values are of different types – int, string, long, and char. Using the “cout” statement, we print all the defined values on the console. Let us see the output of the program in the following snapshot:

The output screenshot clearly showcases the use of a “typedef” with the struct that contains multiple data types to create an alias for a structure. It provides a more concise, readable, and simpler way to work with the structs in the complete C++ program.


To summarize the “typedef” struct in C++, “typedef” is a keyword that is used in C++ to create aliases of primitive, built-in, or user-defined data types. Paired with the “struct” keyword, “typedef” is a powerful tool to enhance the code conciseness and clarity. The “typedef” definition usually helps reduce the lines of code and memory areas. However, too much use of “typedef” is not recommended in any program, neither short nor long, and complicated projects because it can create ambiguity. In this article, we explored about the “typedef” struct with the help of straightforward examples to understand the working, implementation, and usage of “typedef” in C++ programs.

About the author

Kalsoom Bibi

Hello, I am a freelance writer and usually write for Linux and other technology related content