A Comprehensive Guide to Constructors in C++: Everything You Need to Know
Last Updated :
12 Jul, 2024
In C++, constructors are special member functions of a class that are automatically called when an object of the class is created. They are used to initialize objects. Constructors have the same name as the class and do not have a return type.
What is a Constructor?
A constructor is a special member function of a class that initializes objects of that class. Constructors are called automatically when an object is created. They have the same name as the class and no return type, not even void.
Example:
class MyClass {
public:
MyClass() {
// Constructor code in C++
}
};Getting Started with Constructors in C++
Syntax and Basic Rules of Constructors in C++
- Constructors must have the same name as the class.
- They cannot have a return type.
- Constructors can be overloaded.
- Constructors are called automatically when an object is created.
Example:
C++
#include <iostream>
using namespace std;
class MyClass {
public:
MyClass()
{
cout << "Default constructor called" << endl;
}
MyClass(int a)
{
cout << "Parameterized constructor called with "
"value: "
<< a << endl;
}
};
Types of Constructors
- Default Constructor: A default constructor is a constructor that can be called with no arguments. If no constructors are defined, the compiler generates a default constructor.
- Parameterized Constructor: A parameterized constructor takes arguments to initialize an object with specific values.
- Copy Constructor: A copy constructor initializes an object using another object of the same class. It performs a deep copy, creating a new instance with the same values.
- Move Constructor: Introduced in C++11, a move constructor transfers resources from a temporary object to a new object, which can improve performance by eliminating unnecessary copying.
- Destructors: A destructor is a special member function that is executed when an object goes out of scope or is explicitly deleted. Destructors have the same name as the class, preceded by a tilde (~), and are used to release resources allocated by the object.
Example:
Default Constructor
#include <iostream>
using namespace std;
class MyClass {
public:
MyClass() {
cout << "Default constructor called" << endl;
}
};
int main() {
MyClass obj; // Default constructor is called
return 0;
}
#include <iostream>
using namespace std;
class MyClass {
private:
int x;
public:
MyClass(int val) : x(val) {
cout << "Parameterized constructor called with value: " << x << endl;
}
};
int main() {
MyClass obj(42); // Parameterized constructor is called
return 0;
}
#include <iostream>
using namespace std;
class MyClass {
private:
int x;
public:
MyClass(int val) : x(val) {}
// Copy constructor
MyClass(const MyClass& other) : x(other.x) {
cout << "Copy constructor called" << endl;
}
void print() {
cout << "x: " << x << endl;
}
};
int main() {
MyClass obj1(42);
MyClass obj2 = obj1; // Copy constructor is called
obj2.print();
return 0;
}
#include <iostream>
#include <vector>
using namespace std;
class MyClass {
private:
vector<int>* data;
public:
MyClass(int size) {
data = new vector<int>(size);
cout << "Constructor called" << endl;
}
// Move constructor
MyClass(MyClass&& other) noexcept : data(other.data) {
other.data = nullptr;
cout << "Move constructor called" << endl;
}
~MyClass() {
delete data;
cout << "Destructor called" << endl;
}
};
int main() {
MyClass obj1(10);
MyClass obj2 = move(obj1); // Move constructor is called
return 0;
}
#include <iostream>
using namespace std;
class MyClass {
public:
MyClass() {
cout << "Constructor called" << endl;
}
~MyClass() {
cout << "Destructor called" << endl;
}
};
int main() {
MyClass obj; // Constructor and then destructor are called
return 0;
}
Importance of Constructors in C++
Constructors are essential because they allow for the initialization of objects, ensuring they start in a valid state. Without constructors, each object’s member variables would have to be set manually after creation, which can lead to errors and increased complexity
Here are some key points highlighting the importance of constructors in C++:
1. Object Initialization:
- Automatic Initialization: Constructors are used to initialize the objects when they are created, ensuring that the objects start in a well-defined state.
- Default Values: They can assign default values to data members, which helps in preventing the use of uninitialized variables.
2. Resource Management:
- Memory Allocation: Constructors can allocate resources such as memory, file handles, or network connections, which the object will manage.
- RAII (Resource Acquisition Is Initialization): This principle ensures that resources are properly acquired and released. The constructor acquires the resources, and the destructor releases them, providing automatic resource management.
3. Overloaded Constructors:
- Multiple Ways to Initialize: A class can have multiple constructors with different parameters, allowing objects to be initialized in various ways depending on the provided arguments.
- Constructor Overloading: This feature enhances flexibility by allowing different methods of object creation.
4. Encapsulation:
- Controlled Initialization: Constructors provide a controlled way to initialize the data members, maintaining encapsulation and data integrity.
- Preventing Invalid States: By using constructors, we can ensure that an object cannot be created in an invalid state, as any necessary validation can be performed within the constructor.
5. Inheritance and Polymorphism:
- Base Class Initialization: In a class hierarchy, constructors are essential for initializing base class parts of derived class objects.
- Virtual Constructors: Though C++ does not support virtual constructors directly, the concept can be achieved through factory methods to create objects of derived classes, facilitating polymorphic behavior.
6. Initialization Lists:
- Efficient Initialization: Constructors can use initialization lists to initialize data members directly, often leading to more efficient code.
- Const Members and References: Initialization lists are necessary to initialize constant data members and references, which cannot be assigned values after the object is created.
Example to show the importance of constructors in C++:
Here’s an example illustrating the importance of constructors in C++:
C++
#include <iostream>
#include <string>
class Person {
std::string name;
int age;
public:
// Default constructor
Person()
: name("Unknown")
, age(0)
{
std::cout << "Default constructor called"
<< std::endl;
}
// Parameterized constructor
Person(std::string name, int age)
: name(name)
, age(age)
{
std::cout << "\nParameterized constructor called"
<< std::endl;
}
// Copy constructor
Person(const Person& p)
: name(p.name)
, age(p.age)
{
std::cout << "\nCopy constructor called" << std::endl;
}
void display() const
{
std::cout << "Name: " << name << ", Age: " << age
<< std::endl;
}
};
int main()
{
Person p1; // Default constructor
p1.display();
Person p2("John", 25); // Parameterized constructor
p2.display();
Person p3 = p2; // Copy constructor
p3.display();
return 0;
}
OutputDefault constructor called
Name: Unknown, Age: 0
Parameterized constructor called
Name: John, Age: 25
Copy constructor called
Name: John, Age: 25
In this example:
- The default constructor initializes the
name to "Unknown" and age to 0. - The parameterized constructor allows initializing
name and age with specific values. - The copy constructor creates a new object as a copy of an existing object.
These constructors ensure that objects of the Person class are always created in a valid state.
1. Constructor Overloading
Constructor overloading allows a class to have more than one constructor with different parameters. This is useful for initializing objects in different ways.
Example:
C++
#include <iostream>
using namespace std;
class MyClass {
private:
int x;
int y;
public:
MyClass() : x(0), y(0) {
cout << "Default constructor called" << endl;
}
MyClass(int a) : x(a), y(0) {
cout << "Parameterized constructor called with one argument" << endl;
}
MyClass(int a, int b) : x(a), y(b) {
cout << "Parameterized constructor called with two arguments" << endl;
}
void print() {
cout << "x: " << x << ", y: " << y << endl;
}
};
int main() {
MyClass obj1;
MyClass obj2(10);
MyClass obj3(10, 20);
obj1.print();
obj2.print();
obj3.print();
return 0;
}
2. Initializer List
An initializer list is a more efficient way to initialize member variables. It is used in the constructor definition.
Example:
C++
#include <iostream>
using namespace std;
class MyClass {
private:
int x;
int y;
public:
MyClass(int a, int b) : x(a), y(b) {
cout << "Constructor with initializer list called" << endl;
}
void print() {
cout << "x: " << x << ", y: " << y << endl;
}
};
int main() {
MyClass obj(10, 20);
obj.print();
return 0;
}
3. Constructor Initialization Order
The order in which constructors initialize member variables is determined by the order of declaration in the class, not the order in the initializer list.
Example:
C++
#include <iostream>
using namespace std;
class MyClass {
private:
int x;
int y;
public:
MyClass(int a, int b) : y(b), x(a) { // x is initialized before y, despite the order in the initializer list
cout << "Constructor called" << endl;
}
void print() {
cout << "x: " << x << ", y: " << y << endl;
}
};
int main() {
MyClass obj(10, 20);
obj.print();
return 0;
}
Advanced Aspects of Constructors
1. Member Initializer Lists
Using member initializer lists is more efficient than assigning values inside the constructor body, especially for complex types or when initializing const or reference members.
Example:
C++
#include <iostream>
using namespace std;
class Complex {
private:
const int id;
int value;
public:
// Using initializer list
Complex(int id, int value) : id(id), value(value) {
cout << "Complex object created with id: " << id << " and value: " << value << endl;
}
void display() const {
cout << "ID: " << id << ", Value: " << value << endl;
}
};
int main() {
Complex c(1, 100);
c.display();
return 0;
}
In this example, the initializer list ensures id is initialized correctly.
2. Delegating Constructors
C++11 introduced delegating constructors, allowing one constructor to call another constructor within the same class. This helps to avoid code duplication.
Example:
C++
#include <iostream>
using namespace std;
class MyClass {
private:
int a, b;
public:
// Delegating constructor
MyClass() : MyClass(0, 0) {
cout << "Default constructor called" << endl;
}
MyClass(int a, int b) : a(a), b(b) {
cout << "Parameterized constructor called with a: " << a << ", b: " << b << endl;
}
void display() const {
cout << "a: " << a << ", b: " << b << endl;
}
};
int main() {
MyClass obj1;
MyClass obj2(10, 20);
obj1.display();
obj2.display();
return 0;
}
Here, the default constructor delegates to the parameterized constructor.
3. Explicit Constructors
The explicit keyword prevents implicit conversions, which can lead to unexpected behavior.
Example:
C++
#include <iostream>
using namespace std;
class MyClass {
private:
int value;
public:
// Explicit constructor
explicit MyClass(int value) : value(value) {
cout << "Explicit constructor called with value: " << value << endl;
}
void display() const {
cout << "Value: " << value << endl;
}
};
void process(const MyClass& obj) {
obj.display();
}
int main() {
MyClass obj(42);
process(obj);
// process(42); // Error: No implicit conversion allowed
return 0;
}
Using explicit prevents implicit conversion from int to MyClass.
4. Constructor Inheritance
C++11 introduced constructor inheritance, allowing derived classes to inherit constructors from base classes.
Example:
C++
#include <iostream>
using namespace std;
class Base {
public:
Base(int x) {
cout << "Base constructor called with x: " << x << endl;
}
};
class Derived : public Base {
public:
using Base::Base; // Inherit constructor
Derived(int x, int y) : Base(x) {
cout << "Derived constructor called with y: " << y << endl;
}
};
int main() {
Derived d1(10); // Calls Base(int)
Derived d2(20, 30); // Calls Derived(int, int)
return 0;
}
In this example, the Base class constructor is inherited by the Derived class.
5. Smart Pointers and RAII
Using smart pointers (like std::unique_ptr and std::shared_ptr) with constructors ensures proper resource management following the RAII (Resource Acquisition Is Initialization) principle.
Example:
C++
#include <iostream>
#include <memory>
using namespace std;
class Resource {
public:
Resource() {
cout << "Resource acquired" << endl;
}
~Resource() {
cout << "Resource released" << endl;
}
};
class Manager {
private:
unique_ptr<Resource> resource;
public:
// Constructor
Manager() : resource(make_unique<Resource>()) {
cout << "Manager created" << endl;
}
void useResource() {
cout << "Using resource" << endl;
}
};
int main() {
Manager mgr;
mgr.useResource();
return 0;
}
In this example, unique_ptr ensures that the Resource is properly managed and released.
6. Rule of Three, Rule of Five
Follow these rules to manage resource ownership correctly:
- Rule of Three: If a class needs a custom destructor, copy constructor, or copy assignment operator, it likely needs all three.
- Rule of Five: In addition to the Rule of Three, include the move constructor and move assignment operator for modern C++.
7. Preventing Object Copying
Use the = delete syntax to prevent copying of objects.
Example:
C++
#include <iostream>
using namespace std;
class MyClass {
public:
MyClass() = default;
MyClass(const MyClass&) = delete; // Delete copy constructor
MyClass& operator=(const MyClass&) = delete; // Delete copy assignment operator
};
int main() {
MyClass obj1;
// MyClass obj2 = obj1; // Error: use of deleted function
return 0;
}
8. Singleton Pattern and Constructors
The Singleton pattern ensures a class has only one instance and provides a global point of access to it.
Example:
C++
#include <iostream>
using namespace std;
class Singleton {
private:
static Singleton* instance;
// Private constructor to prevent instantiation
Singleton() {}
public:
static Singleton* getInstance() {
if (!instance) {
instance = new Singleton();
}
return instance;
}
};
Singleton* Singleton::instance = nullptr;
int main() {
Singleton* s1 = Singleton::getInstance();
Singleton* s2 = Singleton::getInstance();
if (s1 == s2) {
cout << "Both pointers point to the same instance" << endl;
}
return 0;
}
9. Constructors and Exception Safety
Ensure that constructors are exception-safe by properly handling exceptions and ensuring resources are correctly released.
Example:
C++
#include <iostream>
using namespace std;
class MyClass {
private:
int* data;
public:
MyClass(int size) {
data = new int[size];
if (!data) {
throw bad_alloc();
}
}
~MyClass() {
delete[] data;
}
};
Common Mistakes and Pitfalls
Uninitialized Member Variables
Always initialize member variables to avoid undefined behavior.
Example:
C++
#include <iostream>
using namespace std;
class MyClass {
private:
int x;
public:
MyClass() : x(0) {} // Initialize x to 0
};
Infinite Recursion in Constructors
Be careful with constructor delegation to avoid infinite recursion.
Example:
C++
#include <iostream>
using namespace std;
class MyClass {
public:
MyClass() : MyClass() {} // Error: infinite recursion
};
Object Slicing with Copy Constructors
Object slicing occurs when a derived class object is copied to a base class object.
Example:
C++
#include <iostream>
using namespace std;
class Base {
public:
int x;
};
class Derived : public Base {
public:
int y;
};
int main() {
Derived d;
Base b = d; // Object slicing: only Base part is copied
return 0;
}
Memory Leaks in Constructors
Ensure that allocated resources are properly released to avoid memory leaks.
Example:
C++
#include <iostream>
using namespace std;
class MyClass {
private:
int* data;
public:
MyClass(int size) {
data = new int[size];
}
~MyClass() {
delete[] data;
}
};
Best Practices for Constructors
- Use Initializer Lists: Always prefer initializer lists over assignment in the constructor body for better performance and correctness.
- Minimize Resource Allocation in Constructors: Avoid complex logic or resource allocation directly in constructors. Consider using factory functions or initializing after object creation.
- Use
explicit for Single-Argument Constructors: Prevent unintended implicit conversions by marking single-argument constructors with explicit. - Leverage Smart Pointers: Use smart pointers for managing dynamic resources to ensure automatic cleanup and prevent memory leaks.
- Avoid Code Duplication: Use delegating constructors to avoid code duplication and ensure consistency in initialization logic.
Hands-on Examples and Exercises
1. Practice Problems on Default and Parameterized Constructors
Create a class Rectangle with a default constructor and a parameterized constructor to initialize length and width.
Example:
C++
#include <iostream>
using namespace std;
class Rectangle {
private:
int length;
int width;
public:
Rectangle() : length(0), width(0) {}
Rectangle(int l, int w) : length(l), width(w) {}
void print() {
cout << "Length: " << length << ", Width: " << width << endl;
}
};
int main() {
Rectangle rect1;
Rectangle rect2(10, 20);
rect1.print();
rect2.print();
return 0;
}
2. Implementing and Using Copy Constructors
Create a class Array that implements a copy constructor to perform a deep copy of an array.
Example:
C++
#include <iostream>
using namespace std;
class Array {
private:
int* data;
int size;
public:
Array(int s) : size(s) {
data = new int[size];
}
Array(const Array& other) : size(other.size) {
data = new int[size];
for (int i = 0; i < size; ++i) {
data[i] = other.data[i];
}
}
~Array() {
delete[] data;
}
void print() {
for (int i = 0; i < size; ++i) {
cout << data[i] << " ";
}
cout << endl;
}
};
int main() {
Array arr1(5);
Array arr2 = arr1; // Copy constructor is called
arr1.print();
arr2.print();
return 0;
}
3. Practicing Move Constructors with Real-world Scenarios
Create a class Buffer that implements a move constructor to transfer ownership of a dynamically allocated buffer.
Example:
C++
#include <iostream>
using namespace std;
class Buffer {
private:
char* data;
public:
Buffer(size_t size) {
data = new char[size];
}
Buffer(Buffer&& other) noexcept : data(other.data) {
other.data = nullptr;
}
~Buffer() {
delete[] data;
}
void print() {
if (data) {
cout << "Buffer is not null" << endl;
} else {
cout << "Buffer is null" << endl;
}
}
};
int main() {
Buffer buf1(100);
Buffer buf2 = move(buf1); // Move constructor is called
buf1.print();
buf2.print();
return 0;
}
4. Writing Constructors with Initializer Lists
Create a class Point that uses an initializer list to initialize its member variables.
Example:
C++
#include <iostream>
using namespace std;
class Point {
private:
int x;
int y;
public:
Point(int a, int b) : x(a), y(b) {}
void print() {
cout << "x: " << x << ", y: " << y << endl;
}
};
int main() {
Point p(10, 20);
p.print();
return 0;
}
5. Exercises on Constructor Overloading
Create a class Circle with overloaded constructors to initialize the radius in different ways.
Example:
C++
#include <iostream>
using namespace std;
class Circle {
private:
double radius;
public:
Circle() : radius(0) {}
Circle(double r) : radius(r) {}
void print() {
cout << "Radius: " << radius << endl;
}
};
int main() {
Circle c1;
Circle c2(5.5);
c1.print();
c2.print();
return 0;
}
Summary and Conclusion
Key Takeaways
- Constructors initialize objects, ensuring they start in a valid state.
- Multiple types of constructors (default, parameterized, copy, move) serve different initialization purposes.
- Destructors clean up resources when objects go out of scope.
Recap of Important Concepts
- Constructors and destructors are vital for managing resource allocation and deallocation.
- Initializer lists provide an efficient way to initialize member variables.
- Move constructors improve performance by eliminating unnecessary copying.
Final Words on Constructors in C++
Understanding constructors and destructors is essential for writing robust and efficient C++ programs. Proper use of these special member functions ensures that objects are initialized and cleaned up correctly, which is critical for resource management and overall program stability.
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Type Conversion in C++Type conversion means converting one type of data to another compatible type such that it doesn't lose its meaning. It is essential for managing different data types in C++. Let's take a look at an example:C++#include <iostream> using namespace std; int main() { // Two variables of different t
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Casting Operators in C++The casting operators is the modern C++ solution for converting one type of data safely to another type. This process is called typecasting where the type of the data is changed to another type either implicitly (by the compiler) or explicitly (by the programmer).Let's take a look at an example:C++#
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C++ Operators
Operators in C++C++ operators are the symbols that operate on values to perform specific mathematical or logical computations on given values. They are the foundation of any programming language.Example:C++#include <iostream> using namespace std; int main() { int a = 10 + 20; cout << a; return 0; }Outpu
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C++ Arithmetic OperatorsArithmetic Operators in C++ are used to perform arithmetic or mathematical operations on the operands (generally numeric values). An operand can be a variable or a value. For example, ‘+’ is used for addition, '-' is used for subtraction, '*' is used for multiplication, etc. Let's take a look at an
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Unary Operators in CIn C programming, unary operators are operators that operate on a single operand. These operators are used to perform operations such as negation, incrementing or decrementing a variable, or checking the size of a variable. They provide a way to modify or manipulate the value of a single variable in
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Bitwise Operators in CIn C, bitwise operators are used to perform operations directly on the binary representations of numbers. These operators work by manipulating individual bits (0s and 1s) in a number.The following 6 operators are bitwise operators (also known as bit operators as they work at the bit-level). They are
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Assignment Operators in CIn C, assignment operators are used to assign values to variables. The left operand is the variable and the right operand is the value being assigned. The value on the right must match the data type of the variable otherwise, the compiler will raise an error.Let's take a look at an example:C#include
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C++ sizeof OperatorThe sizeof operator is a unary compile-time operator used to determine the size of variables, data types, and constants in bytes at compile time. It can also determine the size of classes, structures, and unions.Let's take a look at an example:C++#include <iostream> using namespace std; int ma
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Scope Resolution Operator in C++In C++, the scope resolution operator (::) is used to access the identifiers such as variable names and function names defined inside some other scope in the current scope. Let's take a look at an example:C++#include <iostream> int main() { // Accessing cout from std namespace using scope // r
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C++ Input/Output
C++ Control Statements
Decision Making in C (if , if..else, Nested if, if-else-if )In C, programs can choose which part of the code to execute based on some condition. This ability is called decision making and the statements used for it are called conditional statements. These statements evaluate one or more conditions and make the decision whether to execute a block of code or n
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C++ if StatementThe C++ if statement is the most simple decision-making statement. It is used to decide whether a certain statement or block of statements will be executed or not executed based on a certain condition. Let's take a look at an example:C++#include <iostream> using namespace std; int main() { int
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C++ if else StatementThe if statement alone tells us that if a condition is true it will execute a block of statements and if the condition is false, it won’t. But what if we want to do something else if the condition is false. Here comes the C++ if else statement. We can use the else statement with if statement to exec
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C++ if else if LadderIn C++, the if-else-if ladder helps the user decide from among multiple options. The C++ if statements are executed from the top down. As soon as one of the conditions controlling the if is true, the statement associated with that if is executed, and the rest of the C++ else-if ladder is bypassed. I
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Switch Statement in C++In C++, the switch statement is a flow control statement that is used to execute the different blocks of statements based on the value of the given expression. It is a simpler alternative to the long if-else-if ladder.SyntaxC++switch (expression) { case value_1: // code to be executed. break; case v
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Jump statements in C++Jump statements are used to manipulate the flow of the program if some conditions are met. It is used to terminate or continue the loop inside a program or to stop the execution of a function.In C++, there is four jump statement:Table of Contentcontinue Statementbreak Statementreturn Statementgoto S
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C++ LoopsIn C++ programming, sometimes there is a need to perform some operation more than once or (say) n number of times. For example, suppose we want to print "Hello World" 5 times. Manually, we have to write cout for the C++ statement 5 times as shown.C++#include <iostream> using namespace std; int
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for Loop in C++In C++, for loop is an entry-controlled loop that is used to execute a block of code repeatedly for the given number of times. It is generally preferred over while and do-while loops in case the number of iterations is known beforehand.Let's take a look at an example:C++#include <bits/stdc++.h
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Range-Based for Loop in C++In C++, the range-based for loop introduced in C++ 11 is a version of for loop that is able to iterate over a range. This range can be anything that is iteratable, such as arrays, strings and STL containers. It provides a more readable and concise syntax compared to traditional for loops.Let's take
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C++ While LoopIn C++, the while loop is an entry-controlled loop that repeatedly executes a block of code as long as the given condition remains true. Unlike the for loop, while loop is used in situations where we do not know the exact number of iterations of the loop beforehand as the loop execution is terminate
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C++ do while LoopIn C++, the do-while loop is an exit-controlled loop that repeatedly executes a block of code at least once and continues executing as long as a given condition remains true. Unlike the while loop, the do-while loop guarantees that the loop body will execute at least once, regardless of whether the
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C++ Functions
Functions in C++A Function is a reusable block of code designed to perform a specific task. It helps break large programs into smaller, logical parts. Functions make code cleaner, easier to understand, and more maintainable.Just like in other languages, C++ functions can take inputs (called parameters), execute a b
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return Statement in C++In C++, the return statement returns the flow of the execution to the function from where it is called. This statement does not mandatorily need any conditional statements. As soon as the statement is executed, the flow of the program stops immediately and returns the control from where it was calle
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Parameter Passing Techniques in CIn C, passing values to a function means providing data to the function when it is called so that the function can use or manipulate that data. Here:Formal Parameters: Variables used in parameter list in a function declaration/definition as placeholders. Also called only parameters.Actual Parameters
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Difference Between Call by Value and Call by Reference in CFunctions can be invoked in two ways: Call by Value or Call by Reference. These two ways are generally differentiated by the type of values passed to them as parameters.The following table lists the differences between the call-by-value and call-by-reference methods of parameter passing.Call By Valu
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Default Arguments in C++A default argument is a value provided for a parameter in a function declaration that is automatically assigned by the compiler if no value is provided for those parameters in function call. If the value is passed for it, the default value is overwritten by the passed value.Example:C++#include <i
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Inline Functions in C++In C++, inline functions provide a way to optimize the performance of the program by reducing the overhead related to a function call. 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
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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 <iostream> using namespace std; i
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C++ Pointers and References
Pointers 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
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C++ PointersA pointer is a special variable that holds the memory address of another variable, rather than storing a direct value itself. Pointers allow programs to access and manipulate data in memory efficiently, making them a key feature for system-level programming and dynamic memory management. When we acc
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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
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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
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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
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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
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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
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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
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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
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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
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