Question

Consider the following program written in C syntax

int a , b , c ; // first declaration

void g()
{
print(a,b,c);
}
int f(int a) // parameter declaration
{

int b; // second declaration
b = a + 1;
g(); // first call
{

int a; // third declaration
int c; // fourth declaration
c = b;
a = b + c;
g(); // second call
}
g(); // third call
return a + b ;
}

int main()
{
int a = 2; // fifth declaration
a = f(a);
g(); // fourth call
}

1. If static scoping is used, the reference to a in the first call to g() resolves to which declaration?
2. If static scoping is used, the reference to a in the third call to g() resolves to which declaration?
3. If dynamic scoping is used, the reference to a in the first call to g() resolves to which declaration?
4. If dynamic scoping is used, the reference to a in the third call to g() resolves to which declaration?
5. What is the output of this program if static scoping is used?
6. What is the output of this program is dynamic scoping is used?

Answer 1

1. Reference to first declaration. It is because only the binding is done at compile time. Hence, it always refers to global variable. Also, the g() is a global function.

2. Reference to first declaration. It is same as above, because binding is only done at compile time. Hence, it refers to first declaration.

3. Reference to fifth declaration. Dynamic binding always uses last declaration in a recent call.

4. Reference to third declaration. As we know, dynamic binding always uses last declaration in a recent call. Here, third call resolves the reference to third declaration.

5. NOTE: At the time of declaration, the global variables are initialized to 0.

OUTPUT:

000                // It refers first declaration in first call 000               // g() refers to first declaration in static. 000              // third call of g() 000               // fourth call of g()

6. Output:

230            // In first call of g(), a=2 by last declaration before the call, b=a+1=3 and                   // c = 0 Garbage    // in second call of g(), a and b are not initialized and, they are non-static. 230           // g(), third call 500           // g() fourth call