Sample Midterm

1. What are all possible outputs of the following code fragment?

   void f(int a, int b)
   {
   		printf("%d %d\n", a, b);
   }
    
   void main(void)
   {
   		int i = 5;
   		f(++i, ++i);
   }
   

2. Given the definitions

   		int numbs[10];
   		int *ptr = numbs;
   

   which of the following are equivalent, and why?
   1. numbs[3]
   2. numbs + 3
   3. * ( numbs + 3 )
   4. * ( ptr + 3 )
   5. *ptr + 3
3. Write a recursive function to add the integers from a to b. You may assume that a ≤ b initially.
4. Use the following code fragment to answer parts a, b, and c:

   for(x = i = 0; i <= 100; i += 2, x += i);
   

   1. In one short sentence , what does this for loop do?
   2. Is the following while loop equivalent? If not, how does its result differ?

      		x = i = 0;
      		while( i++ = 100)
      			x += ++i;
      

   3. Does the following for loop do the same thing? If not, what does it do?

      		for(x = i = 0; i <= 100; i++){
      			if (!(i % 2))
      				continue;
      			x = x + i;
      		}
      

5. What does the following function do?

   		int x(char *s, char *t)
   		{
   			for( ; *s == *t; s++, t++)
   				if (*s == '\0')
   					return(0);
   			return(*s - *t);
   		}
   

6. What does this function do?

   char *x(char *s, char c)
   {
   		char *r = NULL;
    
   		do{
   			while(*s && *s != c) s++;
   			if (*s) r = s; 
   		} while(*s++);
   		return(r);
   }
   

7. The following segment of code is supposed to print the number of times the routine a_again is called. Yet, regardless of the input, it prints 0. Why? How would you fix it?

   void a_again(int acount)
   {
   		++acount;
   }
    
   void main(void)
   {
   		register int c;
   		int counter = 0;
    
   		while((c = getchar()) != EOF)
   					if (c == 'a' || c == 'A')
   				a_again(counter);
    
   		printf("%d\n", counter);
   		exit(0);
   }
   

---

ECS 153, Introduction to Computer Security Winter Quarter 2002 Email: [email protected]