Consider the following two C++ programs P₁ and P₂ and two statements S₁ and S₂ about the programs:

P1	P2
void f(int a, int*b, int &c) {     a = 1;        *b =2;        c = 3; } int main () {        int i = 0;       f(i, &i, i):       cout ≪ i; }	double a = 1, b =2; double &f(double &d) {       d = 4;          return b; } int main () {       f(a) = 5;       cout ≪ a ≪ “:” ≪b; }

 

S₁: P₁ prints out 3

S₂: P₂ prints out 4:2

What can you say about the statement S₁ and S₂? 

Code P₁:

In function f, there are three parameters, one is integer, second is pointer , third is reference variable. When there is call to function f from main in which initially value of i = 0

Int main ()

{int i= 0; f(i, &i, i); cout<< i;}           /it calls the function f

void f (int a, int *b, int &c)

{

a =1;      /it changes the value of i to 1, but it is call by value, change will not reflect back to main

*b = 2;      / it changes the value of i to 2 and change will reflect to main function

c = 3;         / it changes the value of i again and final value becomes 3.

}

So, Code p₁ prints out 3.

Code P₂:

In this, f(a) calls the function f which is:

double &f(double &d)

{

d =4;          / it will update the value of a to 4 and returns reference to double b.

return b;             / here it returns the value of b as 5.

}

So, in main

int main ()

{

f(a) = 5;            / a becomes 4

cout<< a<< “:”<< b;        / it prints 4: 5

}