Primitives → Passed by value (copy of the value). Objects → Passed by value (copy of the reference)

Sivaram Rasathurai

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Mar 28, 2025

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What is Pass-by-Reference?

• You send a reference (memory address) to the method.
• If the method changes the value, it modifies the original variable.

c++ code

#include <iostream>
using namespace std;

void modifyNumber(int &x) { // x is passed by reference.
    x = 10;  // Changes original value
}

int main() {
    int a = 5;
    modifyNumber(a);
    cout << a << endl;  // Output: 10
    return 0;
}

What is Pass-by-Value?

• Pass-by-value means Java sends a copy of the value to a method.
• If you change the value inside the method, the original value doesn’t change.

python code

x =5 

def modifyNumber(x):
    x = 10
    
modifyNumber(x)
print(x) # x = 5

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