What happend with my code I don't know

Question

// Without arguments and with return value :
int Sum(); /* Declaration of Function */

/*Other Code*/
int Sum()
{

int x,y,z;
printf("Enter no. 1 : \t");
scanf("%d",&x);
printf("\nEnter no. 2 : \t");
scanf("%d",&y );
z=x+y;
return z;
}

Answer 1

Your code hasn't problems, apart that in C, there is always a main() function that returns an int, this functions is executed when the programs start so your code must be :

// Without arguments and with return value :
int Sum(); /* Declaration of Function */

int main() {
printf("\nThe result is : %d", Sum());
return 0;
}

/*Other Code*/
int Sum()
{

int x,y,z;
printf("Enter no. 1 : \t");
scanf("%d",&x);
printf("\nEnter no. 2 : \t");
scanf("%d",&y );
z=x+y;
return z;
}