Day#85 C' Coding Challenge

What is the difference between Call by Value and Call by Reference?

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• Call by Value and Call by Reference are two ways to invoke functions in C programming
• When call by value is used, the argument passed as value and any processing on this argument doesn't impact the actual value of the argument. This meant a local instance of the argument is created
• Call be value example is as follows

int a = 0,b = 0;

func(a, b);

func(int a,int b)

{

    a = 1;

    b = 2;

}

In the above example, when a,b are passed, a copy of a,b are created and further processing of a,b happens, a,b in func() are local to that function and doesn't impact the a,b used in the calling function.

• In Call by value, we can say that a copy of the variable is passed
• The arguments passed from calling function are called actual arguments and arguments in the called function are called formal arguments
• Call by reference is nothing but which passes a reference of the variable which is nothing but address. When address is passed, the actual value of the variable can be changed unlike the call by value
• Call by reference can be explained by simple example below

int a = 0;

int *ptr = &a;

func(ptr);

func(int *ptr)

{

    *ptr = 1;

}

• In the above example ptr is a pointer and points to the address of a. This ptr is passed through function func().  As *ptr points to the value at the address of a, when *ptr is changed, the actual value of a is changed