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

Date: December 16th, 2009
Time: 14:10-16:00
Open book; turn off computer & mobile phone

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

   #include <iostream>
   int main() // Understanding bitwise operators.
   {
         unsigned s = 2009;
   
         int i = (s >> 5) & ~(~0 << 4);
         std::cout << i << std::endl;
   }

2. What will be the output of the following program?
   
   #include <stdio.h>
   main()
   {
       int b=3;
       int arr[]={6,7,8,9,10};
       int *ptr=arr;
       *(ptr++)+=123;
       printf( "%d,%d\n ",*ptr,*(++ptr));
       // Note that printf() evaluates parameters from the right to the left.
   }
   
   
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>     // Reference to a variable
   

   using std::cout;
   using std::endl;
   
   int main()
   {
       int value = 10;
       int& rvalue = &value;
        value += 5;
       cout << value + rvalue << endl;
   }

   
   
4. 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.

   // Checksum
   #include <iostream>
   using std::cout;
   using std::endl;
   
   int main()
   { int cksum;
     char *p;
     char buf[8192] = "DECEMBER";
   
           /*
            * 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);
   }

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

   // String pointers vs. string arrays.
   #include <iostream>
   
   using std::cout;
   using std::endl;
   
   int main()
   {
       char str[10] = "Discovery";
       char* p = str;
       cout << str << endl;
       cout << p++ << endl;
       for ( ; *p != '\0'; p++)
           *p ^= 0x20;
       cout << p << endl;
       cout << str << endl;
   }
   

6. Show the output of the following program.
   
   // Convert lowercase characters to uppercase
   #include <iostream>
   using std::cout;
   using std::cin;
   using std::endl;
   
   int main()
   {
           // Compare the statement with string "QUIT"
           char pStatement[] = "question";
           char pstr1[] = "QUIT";
           char* p1=pStatement;
           char* p2=pstr1;
           bool flag = true;
           while (flag && *p1 != '\0')
           {
               if (*p1>=97 && *p1<=122)
                   *p1 -= 32;      // Convert to uppercase
               if (*p1 != *p2)
                   flag = false;
               p1++; p2++;
           }
           if (flag && *p2 != '\0')
               flag = false;
           if (flag || *pStatement == '\0')
              cout << "This command is QUIT." << endl;
           else
              cout << "The command " << pStatement << " is not QUIT." << endl;
   }
   
   

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

   // Increment operator & for-loop
   #include<iostream>
   using std::cout;
   using std::endl;
   
   main()
   { int a,x;
     for(a=0,x=0; a<=2 && !x++; a++)
     {
           a++;
     }
     cout << a << x << endl;
   }
   

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

   #include <iostream>
   
   int main()	// break in a nested loop
   {
       for (int i = 1; i < 6; i++) 
   	for (int j = 1; j < 6; j++)
   	{
   		if (j==3)
   			break;
   		std::cout << i << std::endl;
   	}
   }
   

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.

   // dec2bin.c
   #include <iostream>
   using std::cout;
   using std::endl;
   
   void binary(int n, char *s)
   {
       int i = 0;
       if (n>1)
       {
          binary(n/2, s);
          s[i++] = '0' + n % 2;
       }
       else
          s[i++] = '0' + 1;
   }
   
   int main()
   {
       char binary_string[16] = { 0 };
       short a = 2009;
       binary(a, binary_string);
       cout << binary_string << endl;
       return 0;
   }
   

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.
    

    // dec2bin.c
    // Hint: This program slightly differs from the previous one.
    #include <iostream>
    using std::cout;
    using std::endl;
    
    void binary(int n, char *s)
    {
        static int i = 0;
        if (n>1)
        {
           binary(n/2, s);
           s[i++] = '0' + n % 2;
        }
        else
           s[i++] = '0' + 1;
    }
    
    int main()
    {
        char binary_string[16] = { 0 };
        short a = 2009;
        binary(a, binary_string);
        cout << binary_string << endl;
        return 0;
    }