Mid-term Exam (1)
Introduction to Computer Science
NCNU CSIE

Date: October 23rd, 2012
Time: 14:10-16:00
Open book; turn off computer & mobile phone

1. (10%) Consider the following binary representation of a signed short integer (stored in one's complement).  Convert it to a decimal number.

   11000000 11000000

2. (10%) Represent 336.1875 in IEEE single-precision floating-point format.

3. (10%) What will be the output of the following program?
   
   // for-loop
   #include <iostream>
   using std::cout;
   using std::endl;
   
   int main()
   {
       const int max(4);
       int i, j, k;
       for (i=1; i<=max; i++)
           for (j=0; j<=i; j++)
           {
               for (k=0; k<max-j; k++)
                   cout << ' ';
               for (k=0; k<2*j+1; k++)
                   cout << '*';
               cout << endl;
           }
       for (i=1; i<max; i++)
       {
           for (j=1; j<max; j++)
               cout << ' ';
           cout << "***" << endl;
       }
       return 0;
   }
   
   
   
   
4. (10%) What will be the output of the following program?
   
   // Scope
   #include <iostream>
   using std::cout;
   using std::endl;
   
   int main()
   {
       int a=1, b=2, c=3;
       int i;
       for (i=1; i<3; i++)
       {
           static int a=10, c=30;    // P.96
           a = b = c++;
           cout << a << ' ' << b << ' ' << c << endl;
       }
       cout << a << ' ' << b << ' ' << c << endl;
       return 0;
   }
   
   
   
5. (10%) What will be the output of the following program?
   
   // overflow
   #include <iostream>
   int main()
   {
       signed char a(3);
       for (int i=0; i<4; ++i, a = 4*a + 3)
           ;
       std::cout << static_cast<signed int>(a) << std::endl;
       return 0;
   }
   
   
6. (10%) What will be the output of the following program?
   
   // static-cast
   #include <iostream>
   using std::cout;
   using std::endl;
   
   int main()
   {
       char c1, c2 = 'H'; // ASCII code of 'H' is 72;
       cout << (c1 = c2++) << endl;
       cout << static_cast<short>(c1, c2) << endl;
       return 0;
   }
   
   
   

7. (10%) Determine whether the following code has syntax erros or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
   
   // increment and decrement
   #include <iostream>
   using std::endl;
   using std::cout;
   
   int main()
   {
       unsigned short a = 100, b = 200, c = 300;
       cout << (a++, b = --c) << endl;
       cout << a << ' ' << b << ' ' << c << endl;
       return 0;
   }
   

8. (10%) Determine whether the following code has syntax erros or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).

   // Conditional operator
   #include <iostream>
   using std::cout;
   using std::endl;
   
   int main()
   {
       unsigned short n = 23;
       do {
           cout << n << ' ';
           if (n == 1)
               break;
       } while ( n = n % 2 ? 3 * n + 1 : n / 2 );
       return 0;
   }
   
   

9. (10%) Determine whether the following code has syntax erros or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).

   // break vs. continue
   #include <iostream>
   using std::cout;
   using std::endl;
   
   int main()
   {
       int i;
       for (i=1; i<10; i++)
       {
           if (i>2)
               if (i==5)
                   break;
               else
                   continue;
           cout << i << endl;
       }
       cout << i << endl;
       return 0;
   }
   

10. (10%) 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.
    

    // exchange_sort.cpp 
    #include <iostream>
    #include <iomanip>
    using std::cin;
    using std::cout;
    using std::endl;
    using std::setw;
    
    int main()
    {
    	const int MAX = 4;
    	int data[MAX] = { 2, 3, 1, 0};
    	int i, j, temp;
    
    	for (j=0; j<=MAX-2; j++)
    	{
    		for (i=j+1; i<=MAX-1; i++)
    		{
    			if (data[j] > data[i])
    			{
    				temp = data[j]; data[j]=data[i]; data[i]=temp;
    			}
    		}
            	
    		cout << endl << "Round " << j+1 << ":\t";
    		for (i=0; i<MAX; i++)
    		    cout << data[i] << '\t';
    		
    	}
            return 0;
    }

11. (10%) 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.
    

    // Array
    #include <iostream>
    using std::cout;
    using std::endl;
    
    int main()
    {
        int y = 2012;
        int day = ( y-1 + y/4 - y/100 + y/400) % 7;
        int month_days[13] = { 0,
            31, 28, 31, 30, 31, 30,
            31, 31, 30, 31, 30, 31 };
        char weekdays[][10] = { "Sunday", "Monday",
            "Tuesday", "Wednesday", "Thursday",
            "Friday", "Saturday" };
        int m = 10, d = 23;
        int i;
    
        if ( y % 4 == 0 ) month_days[2] = 29;    // leap year
        if ( y % 100 == 0 && y % 400 != 0 ) month_days[2] = 28;
    
        cout << "day = " << day << endl;
        for (i=1; i<m; i++)
            day += month_days[i];
        day += d -1;
    
        cout << "Today is " << weekdays[ day % 7 ] << endl;
        cout << "day = " << day << endl;
        return 0;
    }