typedef in C++ Last Updated : 26 May, 2025 Comments Improve Suggest changes Like Article Like Report The typedef keyword in C++ is used for aliasing existing data types, user-defined data types, and pointers to a more meaningful name. Typedefs allow you to give descriptive names to standard data types, which can also help you self-document your code. Mostly typedefs are used for aliasing, only if the predefined name is too long or complex to write again and again. The unnecessary use of typedef is generally not a good practice.Syntax: C++ typedef current_name new_nam ExampleBelow is the C++ Program to demonstrate typedef: C++ #include <bits/stdc++.h> using namespace std; int main() { // Giving new name // of vector<int> typedef vector<int> vInt; // vec1 is a vector of // type int vInt v; v.push_back(190); v.push_back(180); v.push_back(10); v.push_back(10); v.push_back(27); for (auto X : v) { cout << X << " "; } return 0; } Output190 180 10 10 27 Applications of typedef in C++typedef in C++ can be used for aliasing predefined data types with long names.It can be used with STL data structures like Vectors, Strings, Maps, etc.typedef can be used with arrays as well.We can use typedef with normal pointers as well as function pointers.Using typedef with predefined data typestypedef can be used for aliasing predefined data types like int, char, float, and their derivatives like long, short, signed, and unsigned. The new alias can then be used for making new variables of respective types.Example: C++ #include <iostream> using namespace std; int main() { // Giving the new name to // predefined data type typedef long long ulli; // ulli used to make // long long variables ulli a = 1232133 ; cout << a; return 0; } Output1232133Using typedef with STL data structurestypedef can also be used with STL Data Structures, like Vectors, Strings, Maps, etc. If we are one of those, who do not want to import the entire std namespace in our code, then we need to write std::vector, std::string, etc, again and again. Thus using typedef, in this case, can be a quick way to prevent this and keep our code clean and readable.Example: C++ #include <bits/stdc++.h> using namespace std; int main() { // Give the new name to // map<int, string> typedef map<int, string> mp; mp m {{1, "Geeks"}, {2,"For"}, {3,"Geeks"}}; for (auto& p : m) cout << p.first << " " << p.second << "\n"; return 0; } Output1 Geeks 2 For 3 Geeks Using typedef with arraystypedef can be used with arrays for making newer arrays (just like using them with STL data structures). We can easily make new arrays or make arrays of arrays using typedef with arrays, while keeping our code readable, seamlessly.After this <alias_name> can now be used for creating arrays of type- <data_type> and size <size>.Example: C++ #include <iostream> using namespace std; int main() { typedef int arr[3]; // Making new 1D array arr array1{ 1 , 1, 1}; cout << "Array output: " << "\n"; for (int i = 0; i < 3; i++) cout << array1[i] << " "; cout << "\n"; cout << "\n"; // Making new 2D array // Matrix is an array of // arrays with size (3X3) arr matrix[3]; for (int i = 0; i < 3; i++) for (int j = 0; j < 3; j++) // Initializing the matrix matrix[i][j] = i * j; cout << "Matrix output: " << "\n"; for (int i = 0; i < 3; i++) { for (int j = 0; j < 3; j++) { cout << matrix[i][j] << " "; } cout << "\n"; } return 0; } OutputArray output: 1 1 1 Matrix output: 0 0 0 0 1 2 0 2 4 Using typedef with pointerstypedef can be used with pointers as well. For faster creation of pointers, and keeping the code readable as well. We can use them with both data pointers as well as function pointers.1. Usage with data pointersBelow is the syntax, and example code for using typedef with data pointers.Syntax: C++ typedef <data_type>* <alias_name> Example C++ #include <iostream> using namespace std; int main(){ int a = 10; int b = 20; // typedef with pointers typedef int* iPtr; iPtr pointer_to_a = &a; iPtr pointer_to_b = &b; cout << "a is: " << *pointer_to_a << "\n"; cout << "b is: " << *pointer_to_b << "\n"; return 0; } Outputa is: 10 b is: 20 2. Usage with function pointers:Below is the syntax, and example code to display the usage of typedef with function pointers.Syntax: C++ typedef <return_type> (*<alias_name>)(<parameter_type>,<parameter_type>,....); Example: C++ #include <bits/stdc++.h> using namespace std; // Normal pointer to a function int (*func_ptr1)(int, int); // Using typedef with pointer // to a function typedef int (*func_ptr2)(int, int); // Function to multiply two numbers int product(int u, int v) { return u * v; } int main(void) { func_ptr1 = &product; // Using typedefed function // pointer for creating new // function pointer "new_func" func_ptr2 new_func_ptr = &product; // Using normal pointer to a function int x2 = (*func_ptr1)(3, 2); // Using the new function pointer int x1 = (*new_func_ptr)(2, 4); cout << x1 << endl; cout << x2; } Output8 6Here, "func_ptr1" is a normal function pointer, while "func_ptr2" is a typedef function pointer and it can be used to create more function pointers taking 2 integers as arguments and with return type "int".Note: "func_ptr2" can no longer be used as an independent function pointer and it can only be used for creating new function pointers which can only point to function returning int and taking two int types as their parameters. 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When a function is specified as inline the whole code of the inline function is inserted or substituted at the point of its call during the compilation instead of us 6 min read Lambda Expression in C++C++ 11 introduced lambda expressions to allow inline functions which can be used for short snippets of code that are not going to be reused. Therefore, they do not require a name. They are mostly used in STL algorithms as callback functions.Example:C++#include <bits/stdc++.h> using namespace s 4 min read C++ Pointers and ReferencesPointers and References in C++In C++ pointers and references both are mechanisms used to deal with memory, memory address, and data in a program. Pointers are used to store the memory address of another variable whereas references are used to create an alias for an already existing variable. Pointers in C++ Pointers in C++ are a 5 min read C++ PointersA pointer is a variable that stores the address of another variable. Pointers can be used with any data type, including basic types (e.g., int, char), arrays, and even user-defined types like classes and structures.Create PointerA pointer can be declared in the same way as any other variable but wit 8 min read Dangling, Void , Null and Wild Pointers in CIn C programming pointers are used to manipulate memory addresses, to store the address of some variable or memory location. But certain situations and characteristics related to pointers become challenging in terms of memory safety and program behavior these include Dangling (when pointing to deall 6 min read Applications of Pointers in CPointers in C are variables that are used to store the memory address of another variable. Pointers allow us to efficiently manage the memory and hence optimize our program. In this article, we will discuss some of the major applications of pointers in C. Prerequisite: Pointers in C. C Pointers Appl 4 min read Understanding nullptr in C++Consider the following C++ program that shows problem with NULL (need of nullptr) CPP // C++ program to demonstrate problem with NULL #include <bits/stdc++.h> using namespace std; // function with integer argument void fun(int N) { cout << "fun(int)"; return;} // Overloaded fun 3 min read References in C++In C++, a reference works as an alias for an existing variable, providing an alternative name for it and allowing you to work with the original data directly.Example:C++#include <iostream> using namespace std; int main() { int x = 10; // ref is a reference to x. int& ref = x; // printing v 5 min read Can References Refer to Invalid Location in C++?Reference Variables: You can create a second name for a variable in C++, which you can use to read or edit the original data contained in that variable. While this may not sound appealing at first, declaring a reference and assigning it a variable allows you to treat the reference as if it were the 2 min read Pointers vs References in C++Prerequisite: Pointers, References C and C++ support pointers, which is different from most other programming languages such as Java, Python, Ruby, Perl and PHP as they only support references. But interestingly, C++, along with pointers, also supports references. On the surface, both references and 5 min read Passing By Pointer vs Passing By Reference in C++In C++, we can pass parameters to a function either by pointers or by reference. In both cases, we get the same result. So, what is the difference between Passing by Pointer and Passing by Reference in C++?Let's first understand what Passing by Pointer and Passing by Reference in C++ mean:Passing by 5 min read When do we pass arguments by pointer?In C, the pass-by pointer method allows users to pass the address of an argument to the function instead of the actual value. This allows programmers to change the actual data from the function and also improve the performance of the program. In C, variables are passed by pointer in the following ca 5 min read Like