Easy tutorial for C / C ++ - Call by address

Easy tutorial for C / C ++ - Call by address

Call by by address :

- This is a way to pass the address value of a variable when calling a function. Let's look at a simple example.

Example Code

#include <iostream>

using namespace std;

void Call_A(int *);

int main() {

     int a ;

     a = 4;

     cout << " Call by by address example " << endl;

     cout <<" (1) In main function  : "<< "  a  = " << a << ", address of a = "<< &a << endl;

     Call_A(&a);

     cout <<" (2) In main function  : "<< "  a  = " << a << ", address of a = "<< &a << endl;

     return 0;

}

void Call_A(int *b){

     *b += 1;

          cout <<"     Call by address   : "<< "  b  = " << *b << ", address of b = "<< &b << endl;

}

- The Call_A function with a parameter which is a pointer variable has been defined. In this case, since the argument of the prototype of the function is a pointer, '*' is added.

- The Call_A function takes an address value (int * b) as an argument and increments the value in this address by one (* b + = 1;). Incremented value and address of pointer variable are printed.

- Declare the integer variable 'a' in the main function and substitute 4. First, we print the value of 'a' and the address of variable 'a'.

- When calling the Call_A function, I gave the address value of the variable 'a' as an argument (Call_A (& a);). And once again the value and address of the variable 'a' are printed.

results :

Call by by address example

 (1) In main function  :   a  = 4, address of a = 0x7fff1012ca1c

        Call by address   :   b = 5, address of b = 0x7fff1012c9e8

 (2) In main function  :   a  = 5, address of a = 0x7fff1012ca1c

- On the first line, "Call by by address example" is printed.

- On the second line, the value (a = 4) and the address value (0x7fff1012ca1c) assigned to the variable 'a' defined by the main function are printed.

- The third line shows the result of the function Call_A created by 'call by address' method. The value of pointer variable 'b' is incremented by 1 (b = 5) and the address value of pointer variable 'b' (0x7fff1012c9e8) is also printed. It is different from the address value of the variable 'a' defined in the main function.

- The last line shows the result of the variable 'a' in the main function. You can see that the value of variable 'a' has been changed to 5. Of course, the address value is the same value as the first line, and only the value stored in 'a' is changed.