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In programming languages, functions can be invoked in two ways: which is known as Call by Value and Call by Reference.
In this tutorial, you will learn,
Call by value method copies the value of an argument into the formal parameter of that function. Therefore, changes made to the parameter of the main function do not affect the argument.
In this parameter passing method, values of actual parameters are copied to function's formal parameters, and the parameters are stored in different memory locations. So any changes made inside functions are not reflected in actual parameters of the caller.
Call by reference method copies the address of an argument into the formal parameter. In this method, the address is used to access the actual argument used in the function call. It means that changes made in the parameter alter the passing argument.
In this method, the memory allocation is the same as the actual parameters. All the operation in the function are performed on the value stored at the address of the actual parameter, and the modified value will be stored at the same address.
void main() { int a = 10, void increment(int); Cout << "before function calling" << a; increment(a); Cout << "after function calling" << a; getch(); void increment(int x) { int x = x + 1; Cout << "value is" << x; }
Output:
before function calling 10 value is 11 after function calling 1-0
Because variable declared 'a'in main() is different from variable 'x' in increment(). In this programme only variable names are similar, but their memory address are different and stored in different memory locations.
Public static void(string args[]) { int a = 10; System.out.println("Before call Value of a = ", a); Void increment(); System.out.println("After call Value of a = ", a); } Void increment(int x) { int x = x + 1; }
Output:
Before call Value of a =10 After call Value of a =11
Because variable declared 'a' in is referencing/ pointing to variable 'a' in main(). Here variable name is different, but both are pointing/referencing to same memory address locations.
Parameters | Call by value | Call by reference |
---|---|---|
Definition | While calling a function, when you pass values by copying variables, it is known as "Call By Values." | While calling a function, in programming language instead of copying the values of variables, the address of the variables is used it is known as "Call By References. |
Arguments | In this method, a copy of the variable is passed. | In this method, a variable itself is passed. |
Effect | Changes made in a copy of variable never modify the value of variable outside the function. | Change in the variable also affects the value of the variable outside the function. |
Alteration of value | Does not allow you to make any changes in the actual variables. | Allows you to make changes in the values of variables by using function calls. |
Passing of variable | Values of variables are passed using a straightforward method. | Pointer variables are required to store the address of variables. |
Value modification | Original value not modified. | The original value is modified. |
Memory Location | Actual and formal arguments will be created in different memory location | Actual and formal arguments will be created in the same memory location |
Safety | Actual arguments remain safe as they cannot be modified accidentally. | Actual arguments are not Safe. They can be accidentally modified, so you need to handle arguments operations carefully. |
Default | Default in many programming languages like C++.PHP. Visual Basic NET, and C#. | It is supported by most programming languages like JAVA, but not as default. |
Pros/benefits of a call by value method:
Pros of using call by reference method:
Here, are major cons/drawbacks of a call by value method:
Here, are major cons of using call by reference method:
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