Call by value vs Call by reference in c++

In C++, there are two main ways to pass arguments to functions: call by value and call by reference. Understanding the difference between them is crucial for writing effective and predictable code. Let's explore each method with examples:

Call by Value:

• When you pass an argument by value, a copy of the value is passed to the function. Any changes made to the argument inside the function only affect the copy, not the original variable.

Example:

C++

void swap_values(int x, int y) {
  int temp = x;
  x = y;
  y = temp;
}

int main() {
  int a = 5, b = 10;
  swap_values(a, b);
  // After the function call, a will still be 5 and b will still be 10
  std::cout << "a: " << a << ", b: " << b << std::endl;
  return 0;
}

Call by Reference:

• When you pass an argument by reference, the function receives the memory address of the original variable. Changes made to the argument inside the function directly modify the original variable.

Example:

C++

void swap_values(int& x, int& y) {
  int temp = x;
  x = y;
  y = temp;
}

int main() {
  int a = 5, b = 10;
  swap_values(a, b);
  // After the function call, a will be 10 and b will be 5
  std::cout << "a: " << a << ", b: " << b << std::endl;
  return 0;
}

Key Differences:

• Value vs. address: Call by value passes a copy of the value, while call by reference passes the memory address.

• Changes after function call: In call by value, changes inside the function affect only the copy, not the original. In call by reference, changes affect the original variable directly.

• Use cases:

• Use call by value for simple arguments, especially when you don't want the function to modify the original variable.

• Use call by reference for modifying large objects (like arrays) efficiently, or when you need the function to directly update the original value.

Remember that using pointers can often be used interchangeably with call by reference, while offering more flexibility and potential complexity.