Palli Sanchay Bank Programmer Written Test: 2018প্রশ্ন ও সমাধান

	Destructor	Constructor
Invoked when	An object is destroyed (goes out of scope / deleted)	An object is created (instantiated)
Name	Same as class name, prefixed with ~ (C++)	Same as class name, no prefix
Arguments	Never takes arguments, cannot be overloaded	Can take arguments, can be overloaded (multiple versions)
Count per class	Exactly one	Can be more than one (overloaded)
Purpose	Releases/frees resources (memory, file handles, connections)	Allocates/initialises resources and sets initial state
Called	Automatically, exactly once per object's lifetime	Automatically, once per object creation

Example (C++):

#include <iostream>
using namespace std;

class FileHandler {
public:
    FileHandler() {                       // constructor: acquire resource
        cout << "File opened\n";
    }
    ~FileHandler() {                      // destructor: release resource
        cout << "File closed\n";
    }
};

int main() {
    FileHandler f;      // constructor runs: "File opened"
    cout << "Working with file...\n";
    return 0;            // destructor runs automatically: "File closed"
}

Output:

File opened
Working with file...
File closed

Exam takeaway: constructor = resource acquisition at birth (overloadable, takes arguments); destructor = resource release at death (single, no arguments) — together they implement the RAII (Resource Acquisition Is Initialization) pattern in C++.