In C++, the struct keyword is used to define a struct, whereas the typedef keyword is used for creating an alias(new name) for existing datatypes and user-defined datatypes like class, struct, and union to give them more meaningful names. In this article, we will learn the differences between a struct and a typedef struct in C++.

Struct in C++ 

The struct keyword in C++ is used to define a structure. A structure is a user-defined composite data type that allows us to combine data of different data types together under a single name.

Syntax to Define a Struct

struct StructName {
     data_type member_name1;
     data_type member_name2;
};

Here,

• StructName is the name of the structure.
• member_name are the members (variables or functions) of the structure.

Example

The below example demonstrates the use of structure in C++.

// C++ program to use struct in C++

#include <iostream>
using namespace std;

// define a struct MyStruct
struct MyStruct {
    int num;
    void increase() { num += 5; }
};

int main()
{
    // create object of MyStruct
   struct MyStruct obj;

    // access variable using dot operator
    obj.num = 5;

    // access member function using dot operator
    obj.increase();

    // printing the value of num
    cout << "Number is: " << obj.num;
}

Number is: 10

Typedef Struct in C++

The typedef struct in C++ is used to define a structure and create an alias for it. This allows us to use the alias instead of the struct keyword when defining variables of the structure type.

Syntax to Define a Typedef Struct

typedef struct {
    // members
} AliasName;

Here,

• AliasName is the alias name for the structure.
• members are the variables or functions of the structure.

Example

The below example demonstrates the use of typedef struct in C++.

// C++ program to use typedef struct in C++

#include <iostream>
using namespace std;

// define a typedef struct MyStruct
typedef struct {
    int num;
    void increase() { num += 5; }
} MyStruct;

int main() {
    // create object of MyStruct
    MyStruct obj;

    // access variable using dot operator
    obj.num = 5;

    // access member function using dot operator
    obj.increase();

    // printing the value of num
    cout << "Number is: " << obj.num;
}

Number is: 10

Difference Between Struct and Typedef Struct in C++

The below table demonstrates the key differences between struct and typedef struct in C++ are: