Pass By Value vs. Pass By Reference

“Pass by value” and “Pass by reference” are terms used in programming to describe how arguments are passed to functions. Here’s a breakdown of the differences:

1. Pass by Value:
   • Definition: When you pass an argument by value, you are passing a copy of the actual data.
   • Memory: A new memory location is allocated for the parameter inside the function, and the value of the argument is copied into this new memory location.
   • Modification: Changes made to the parameter inside the function don’t affect the original argument in the calling function.
   • Typical in: Primitive data types in languages like Java (e.g., int, char, float) and all data types in languages like C (without using pointers).
   • Example (in pseudocode):

function exampleFunction(int a) {
	a = 10;
	}
	
main() {
	int x = 5;
	exampleFunction(x);
	print(x);   // Outputs 5, not 10, because the function modified a copy of x, not x.
}

2. Pass by Reference:
   • Definition: When you pass an argument by reference, you are passing a reference (or a pointer) to the actual data, not the actual data itself.
   • Memory: The function receives a reference to the same memory location as the original argument. No copy is made.
   • Modification: Changes made to the parameter inside the function directly affect the original argument in the calling function.
   • Typical in: Objects in languages like Java and by using pointers or references in languages like C++ or C#.
   • Example (in pseudocode using a hypothetical reference syntax):

function exampleFunction(ref int a) {    a = 10;}main() {    int x = 5;    exampleFunction(ref x);    print(x);   // Outputs 10 because the function modified x directly through its reference.}

Note:
In some languages, like Python, the distinction is a bit nuanced. In Python, everything is passed by object reference. However, the effects of modifying arguments in functions can look like pass by value or pass by reference, depending on the mutability of the data types being used. Immutable types (like integers, strings, and tuples) behave like they’re being passed by value, while mutable types (like lists and dictionaries) behave like they’re being passed by reference.