Mid-Term Exam (2)
Introduction to Computer Science
NCNU CSIE

Date: December 10th, 2008
Time: 14:10-17:00
Open book; turn off computer & mobile phone

1. What will be the output of the following program?

   #include <iostream>
   using std::cout;
   using std::endl;
   
   int main()
   {
     cout << 2 << 2 << 2 << endl;
     cout << (2 << 2 << 2) << endl;
     cout << 2 << (2 << 2) << endl;
     cout << (2 << (2 << 2)) << endl;
   }
   
   

2. What will be the output of the following program?

   #include <iostream>
   int main() // Understanding bitwise operators.
   {
         unsigned s = 1963;
   
         int i = (s >> 3) & ~(~0 << 3);
         std::cout << i << std::endl;
   }

3. Check whether the following program has any mistake. If yes, point out the mistakes and correct them; if no, predict the output of the program.

   #include <iostream>
   using std::cout;
   using std::endl;
   
   int main()
   { int cksum;
     char *p;
     char buf[8192] = "NCNU";
   
           /*
            * Draft 8 POSIX 1003.2:
            *
            *   s = sum of all bytes
            *   r = s % 2^16 + (s % 2^32) / 2^16
            *   cksum = (r % 2^16) + r / 2^16
            */
   
     cksum = 0;
     for (p = buf; *p; ++p)
           cksum += *p; 
   
     cksum = (cksum & 0xffff) + (cksum >> 16);
     cksum = (cksum & 0xffff) + (cksum >> 16);
     cout << cksum << endl;
     return (0);
   }

4. What will be the output of the following program?

   #include <iostream>
   
   int main()
   {
   	char c1 = 'A';
   	std::cout << static_cast<char>(c1 | 0x20) << std::endl;
   	
   	char c2 = 'g';
   	std::cout << static_cast<char>(c2 ^ 0x20) << std::endl;
   
   	c1 ^= c2; 
   	c2 ^= c1;
   	c1 ^= c2;
   	std::cout << static_cast<char>(c1) << " , " 
   		<< static_cast<char>(c2) << std::endl;
   	
   	(c2 >>= 6) <<= 1;
   	c2 |= c2 << (1 << 2);
   	std::cout << static_cast<char>(c2 ^ c1) << std::endl;
   }
   

5. Show the output of the following program.
   
   #include <iostream>
   int main()
   {
           const int MAX = 100;
           int i = 1, sum = 0;
           for ( ; ++i <= MAX; sum += i++)
               ;
           std::cout << std::endl << "sum = " << sum
                    << std::endl << "i = " << i
                    << std::endl;
           return 0;
   }
   

6. What will be the output of the following program?

   // bin2dec.c
   #include <iostream>
   using std::cout;
   using std::endl;
   
   int main()
   {
       char b[] = "11110101011";
       int n=0, i=0;
       while (b[i])
           n = (n<<1) + b[i++] - 48;
       cout << n << endl;
       return 0;
   }
   

7. What will be the output of the following program?

   #include <iostream>
   
   int main()
   {
   	for (int i = 1; i < 6; i++) 
   	{
   		if (i==3)
   			continue;
   		std::cout << i << std::endl;
   	}
   }
   

8. Check whether the following program has any mistake. If yes, point out the mistakes and correct them; if no, predict the output of the program.

   // dec2bin.c
   #include <iostream>
   using std::cout;
   using std::endl;
   
   int main()
   {
       int i=0;
       short a[16] = 1963;
       int k=sizeof(a) / sizeof(a[0]);
       for (i=0; a[i]>1; i++)
       {
           a[i+1] = a[i] / 2;
           a[i] %= 2;
       }
       cout << "i=" << i << endl;
       for (int j=i; j>=0; j--)
           cout << a[j];
       cout << endl;
       return 0;
   }
   

9. Check whether the following program has any mistake. If yes, point out the mistakes and correct them; if no, predict the output of the program.
   
   #include <iostream>
   using std::cout;
   using std::endl;
   
   int main()
   {
       int a=1963, b=828;
       int* pa = &a;
       int* pb = &b;
       int* ptemp = NULL;
   
       cout <<   a << "\t" <<   b << endl;
       cout << *pa << "\t" << *pb << endl;
   
       ptemp = pa; pa = pb; pb = ptemp;
   
       cout <<   a << "\t" <<   b << endl;
       cout << *pa << "\t" << *pb << endl;
   
       return 0;
   }
   
10. Consider the following C++ program:

    #include <iostream>
    #include <iomanip>
    
    using std::cout;
    using std::cin;
    using std::endl;
    using std::setw;
    
    int main()
    {
    	int N = 0;
    	int i, j;
    	do 
    	{
    		cout << "N = ? ";
    		cin >> N;
    		for (i=1; i<=N; i++)
    		{
    			int w =    (1)    ;
    			for (j=N-i; j>=0; j--)
    				cout << "*";
    			cout << setw(w);
    			for (j=N-i; j>=0; j--)
    				cout << "*";
    			cout << endl;
    		}
    
    		for (i=   (2)   ; i>0; i--)
    		{
    			int w =    (3)    ;
    			for (j=N-i; j>=0; j--)
    				cout << "*";
    			cout << setw(w);
    			for (j=N-i; j>=0; j--)
    				cout << "*";
    			cout << endl;
    		}
    	} while (N > 0);
    	return 0;
    }
    
    

    If we want to obatin the following results, what expressions should be filled into the three blanks, respectively?

    N = ? 5
    ***** *****
    ****   ****
    ***     ***
    **       **
    *         *
    **       **
    ***     ***
    ****   ****
    ***** *****
    N = ? 6
    ****** ******
    *****   *****
    ****     ****
    ***       ***
    **         **
    *           *
    **         **
    ***       ***
    ****     ****
    *****   *****
    ****** ******