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

2018

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

Program P1

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;
}

Program P2

double a = 1, b = 2;

double &f(double &d)
{
    d = 4;
    return b;
}

int main()
{
    f(a) = 5;
    cout << a << ":" << b;
}

Statements

  • S1: P1 prints out 3

  • S2: P2 prints out 4:2

Answer: D. Only S1 is true — Program P1 passes the variable i by value, pointer, and reference. The parameter a is passed by value, so its assignment to 1 does not affect i. However, the…

  1. A.

    Neither S1 nor S2 is true

  2. B.

    Only S2 is true

  3. C.

    Both S1 and S2 are true

  4. D.

    Only S1 is true

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Show answer & explanation

Correct answer: D

Program P1 passes the variable i by value, pointer, and reference. The parameter a is passed by value, so its assignment to 1 does not affect i. However, the pointer parameter b points to i, so *b = 2 updates i to 2. The reference parameter c refers directly to i, so c = 3 updates i to 3. Consequently, the program prints 3, making statement S1 true.\nIn Program P2, f(a) modifies the local reference d (which is a alias for global variable a) to 4. The function then returns a reference to the global variable b. When we execute f(a) = 5, we are assigning 5 to the returned reference of b. Thus, a becomes 4 and b becomes 5. The output is "4:5", making statement S2 false.\nSince only S1 is true, the correct option is D.

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