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

Date: December 7th 2012
Time: 09:00-11:00
Open book; turn off computer & mobile phone

1. (10%) What will be the output of the following program?
   
   // printf()
   #include <stdio.h>  // include this for printf()
   
   int main()
   {
       int x = 0x127f;
       float y = 12.7f;   
       printf("%+07d\n%07.2f\n", x, -y);   
       return 0;
   }
   
   
   
2. (10%) What will be the output of the following program?
   
   // strcpy()
   #include <iostream>
   #include <cstring>
   
   using std::cout;
   using std::endl;
   
   int main()
   {
       char str1[] = "Hello- ";
       char str2[ sizeof(str1) ];
       // Can we replace "sizeof" with "strlen"?
       for (int i=0; i<4; i++)
       {
           str1[6] = '0' + i;
           strcpy(str2, str1);
           cout << str2 << endl;
       }
       return 0;
   }

3. (10%) What will be the output of the following program?
   
   // break vs. continue
   #include <iostream>
   using std::cout;
   using std::endl;
   
   int main()
   {
       int i, sum = 0;
       for (i=1; i<10; i++)
       {
           if (i % 2) continue;    // P.146
           sum += i;
       }
       cout << sum << endl;
       return 0;
   }
   
   
   
   
   
   
4. (10%) What will be the output of the following program?
   
   // Recursive function
   #include <iostream>
   
   void f(int n)
   {
       if (n >= 8)
           f(n/8);
       std::cout << n % 8;
       return;
   }
   
   int main()
   {
       f(4735);
       std::cout << std::endl;
       return 0;
   }
   
   
   
   
5. (10%) What will be the output of the following program?
   
   // fopen()
   #include <stdio.h>
   
   int main()
   {
       FILE* fd1;
       FILE* fd2;  
       int n;
     
       for (int i=0; i<10; i++)
           if (i % 2)
           {
               fd1 = fopen("odd.txt", "w");
               fprintf(fd1, "%d\n", i);
               fclose(fd1);
           }
           else
           {
               fd2 = fopen("even.txt", "w");
               fprintf(fd2, "%d\n", i);
               fclose(fd2);
           }
     
       fd1 = fopen("odd.txt", "r");
       while ( fscanf(fd1, "%d", &n) != EOF )
           printf("%d\n", n);
       return 0;
   }
   
   
   
6. (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).
   
   // Pointer to int
   #include <iostream>
   
   using std::cout;
   using std::endl;
   
   int main()
   {
       int number1 = 12;
       int number2 = 04;
       int* pnumber = &number2;
       cout << (*pnumber*=2) << endl;   // Is this a valid expression?
       cout << number1 << number2 << 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).
   
   // Size of a char array
   #include <iostream>
   using std::cout;
   using std::endl;
   
   int main()
   {
       char str[][18] = { "George Washington",
                       "John Adams",
                       "Thomas Jefferson",
                       "James Madison",
                       "James Monroe",
                       "John Quincy Adams"
                      };
       cout << sizeof str[2] << 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).

   // Pointer arithmetic
   #include <iostream>
   using std::cout;
   using std::endl;
   
   int main()
   {
       int data[2][4] = { {1, 3, 5, 7}, {2, 4, 6, 8} };
       int* pnum = &data[0][2];
       cout << *(pnum + 2) - *(pnum - 1) << endl;   
       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).

   // Math function
   #include <iostream>
   #include <cmath>
   
   int rnd(float x)
   { return static_cast<int>( floor(x + 0.5) ); }
   
   int main()
   {
       std::cout << rnd(4.5) << std::endl;   
       return 0;
   }
   

10. (10%) What will be the output of the following program?

    // Pass-by-reference
    #include <stdio.h>
    
    int strlen(char* &s)
    {
        char* p = s;
        while (*p != '\0')
            ++p;
        return p - s;
    }
    
    int main()
    {
        char* str = "Apple";
        int n = strlen(str);
        printf("The length of \"%s\" is %d.\n",
            str, n);
        return 0;
    }