C programs post4

Q 16.)

#include
using namespace std;

class Base {
public:
Base()
{
foo();
}

virtual void f()
{
cout << "\nBase::f is being called\n";
}

void foo()
{
f();
}
};

class Derive : public Base {
public:
virtual void f()
{
cout << "\nDerive::f is being called\n";
}
};

int main()
{
Derive d; //Base::f is being called.. f being virtual.. Why derived f() is not being called..
}

why output is not expected..




Q.17)

int main()
{
int i=10, j=2;
int *ip= &i, *jp = &j;
int k = *ip/*jp;
printf("%d",k);
return 0;
}

Is it a valid c-program ? Give reasons.






Q.18)

int main()
{
float f=5,g=10;
enum{i=10,j=20,k=50};
printf("%d\n",++k);
printf("%f\n",f<<2);
printf("%lf\n",f%g);
printf("%lf\n",fmod(f,g));
}

What is the problem with this code ?





Q.19)

What is the output of this two codes:

int main()
{
signed char i=0;
for(;i>=0;i++) ;
printf("%d\n",i);
}

int main()
{
unsigned char i=0;
for(;i>=0;i++) ;
printf("%d\n",i);
}


Why is the difference?





Q.20)

int main()
{
char i=0;
for(;i>=0;i++) ;
printf("%d\n",i);
}

Is it a valid C program ? Give reasons.