Question

We learned that when calling subprograms or functions that we can pass data to the subprogram or function by ‘value’ or by ‘reference’.   Describe what each approach is, how it works and what the potential security disadvantage is when passing parameters by reference.

Answer 1

By passing by reference we are passing the actual object to the other function . If the called function modifies the value of the passed object , then the actual value gets updated which is not what we always want . This approach my cause the loss of original data .The caller function may not maintain a copy or original data and after the called function returns the control the calling function may treat that data as valid and can continue further execution .

for example

#include <iostream>
using namespace std;


void  checkBalance( double &balance ){

    balance =  balance  * 100 ;


}




int main( ){

    double bank_balance = 1000;
    // here we are passing bank_balance as reference

      checkBalance( bank_balance);


    cout<< "The checked balance  when it is passed by reference "<< bank_balance;

    return 0 ;
}

The checked balance when it is passed by reference 180006 Process finished with exit code

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When we pass by value that means we are passing a copy of an object to the called function . so, even if the called function changes the content of the data ( or passed object )  in its function body , the original data ( object in the calling function)  does not change  . So here data loss or modification does not happen .

for example

#include <iostream>
using namespace std;


void  checkBalance( double balance ){

    // here the balance variable is  a new variable created by this function
    // all modification done to this variable is local and has no impact in the calling
    //function variable ( balance ) in main

    balance =  balance  * 100 ;


}




int main( ){

    double bank_balance = 1000;
    // here we are passing bank_balance as a copy/ pass as a value

    checkBalance( bank_balance);


    cout<< "The checked balance when it is passed by value "<< bank_balance;

  return 0 ;
}

The checked balance when it is passed by value 1000 Process finished with exit code