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

Date: December 30th, 2009
Time: 14:10-16:00
Open book; turn off computer & mobile phone

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

   // Range of an unsigned short integer
   #include <iostream>
   using std::cout;
   
   int main()
   {
           unsigned short f=1;
           unsigned short i=1;
           for (i=1; i<14; i++)
           {
                   f *= i;
                   cout << f << "\n";
           }
           return 0;
   }

2. Wha will be the output of the following program?
   
   // break from a loop
   #include <iostream>
   using std::cout;
   using std::endl;
   
   int main()
   {
           int i;
           for (i=1; i<10; i++)
                   if (i==3) break;
                   cout << i << endl;
           return 0;
   }
   
   
   
3. Check whether the following program has any syntax mistake. If yes, point out the mistakes and correct them; if no, predict the output of the program.
   
   #include <iostream>    // Swap without a temporary variable
   int main()
   {
           char a = 'T';
           char b = 'W';
   
           printf("%c %c\n", a, b);
   
           a ^= b; printf("%x\n", a);
           b ^= a; printf("%x\n", b);
           a ^= b; printf("%x\n", a);
   
           printf("%c %c\n", a, b);
   
           return 0;
   }
   
   
4. Check whether the following program has any syntax mistake. If yes, point out the mistakes and correct them; if no, predict the output of the program.

   #include <iostream>
   using std::cout;
   
   int sum(int arg1 = 10, int arg2 = 20, int arg3 = 30, int arg4 = 40);
   
   int main()
   {
           cout << sum(5, 5) << "\n";
           return 0;
   }
   
   int sum(int arg1, int arg2, int arg3, int arg4)
   {
           return arg1 + arg2 + arg3 + arg4;
   }
   
   

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

   // Ex6_01a.cpp
   #include <iostream>
   using std::cout;
   using std::endl;
   
   long sum(long, long);
   long product(long, long);
   
   int main(void)
   {
           long (*pdo_it) (long, long);
   
           pdo_it = product;
           cout << pdo_it(3,5) << endl;
           pdo_it = sum;
           cout << pdo_it(3,5) << endl;
           return 0;
   }
   
   long product(long a, long b)
   {
           return a*b;
   }
   
   long sum(long a, long b)
   {
           return a+b;
   }
   
   

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

   
   // The conditional operator
   #include <iostream>
   using std::cout;
   
   int odd(int i)
   {
           int j = i % 2;
           return (i=1)?1:0;
   }
   
   int main(void)
   {
           for (int k=1; k<=2; k++)
                   if (odd(k))
                           cout << "Odd\n";
                   else
                           cout << "Even\n";
           return 0;
   }
   
   
   

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

   // Comparing two strings
   #include <iostream>
   using std::cout;
   
   int main()
   {
           char* p1="Q";
           char* p2 = "QUIT";
   
           bool flag = true;
           while (flag && *p1 != '\0')
           {
               if (*p1 != *p2)
                   flag = false;
               p1++; p2++;
           }
   
           if (flag)
               cout << "The two strings are the same.\n";
           else
               cout << "The two strings are different.\n";
   }
   
   

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

   // List_program
   #include <iostream>
   using std::cout;
   
   int main()
   {
       const int MAX_LINE=10;
       const int STATEMENT_WIDTH=80;
       int numbers[MAX_LINE]={ 0 };        // Line number
       int next[MAX_LINE] = { 0 };         // Index of the next line
       char statements[MAX_LINE][STATEMENT_WIDTH];
       int nLines = 0;     // how many lines are kept in memory
   
           strcpy(statements[nLines], "A=10");
           numbers[nLines++] = 10;
           strcpy(statements[nLines], "B=20");
           numbers[nLines++] = 20;
           strcpy(statements[nLines], "C=A+B");
           numbers[nLines++] = 30;
   
           // List_program
   
           for (int i=0; i<nLines; i++)
           {
                   cout << numbers[i] << " ";
                   cout << statements[i] << "\n";
           }
   
           cout << sizeof statements / sizeof statements[0] << "\n";
           return 0;
   }
   
   
   

9. The following code is a little different from Ex6_09, so you can expect that its behavior is also different.Predict its output.
   

   // A program to implement a calculator
   #include <iostream>
   #include <cstdlib>
   #include <cctype>
   using std::cin;
   using std::cout;
   using std::endl;
   
   void eatspaces(char* str);
   int expr(char* str);
   int number(char* str, int& index);
   
   int main()
   {
       char buffer[] = "45 - 5 -4";
       eatspaces(buffer);
       cout << strlen(buffer) << endl;
       cout << buffer << " = " << expr(buffer) << endl;
   }
   
   // Function to eliminate spaces from a string
   void eatspaces(char* str)
   {
       int i = 0;
       int j = 0;
   
       while ((*(str + i) = *(str + j++)) != '\0')
           if (*(str+i) != ' ')
               i++;
       return;
   }
   
   // Function to evaluate an arithmetic expression
   int expr(char* str)
   {
       int value = 0;
       int index = 0;
   
       value = number(str, ++index);
   
       for (;;)
       {
           switch (*(str + index++))
           {
               case '\0':
                   return value;
               case '+':
                   value += number(str, ++index);
                   break;
               case '-':
                   value -= number(str, ++index);
                   break;
               default:
                   cout << endl
                        << "Arrrgh!*#!! There's an error"
                        << endl;
                   exit(1);
           }
       }
   }
   
   // Function to recognize a number in a string
   int number(char* str, int& index)
   {
       int value = 0;
       while(isdigit(*(str + index)))
           value = 10*value + (*(str + index++) - '0');
       return value;
   }
   

10. The following code is slightly different from the above one.  Predict its output.
    
    // A program to implement a calculator
    #include <iostream>
    #include <cstdlib>
    #include <cctype>
    using std::cin;
    using std::cout;
    using std::endl;
    
    void eatspaces(char* str);
    int expr(char* str);
    int number(char* str, int& index);
    
    int main()
    {
        char buffer[] = "45 - 5 -4";
        eatspaces(buffer);
        cout << strlen(buffer) << endl;
        cout << buffer << " = " << expr(buffer) << endl;
    }
    
    // Function to eliminate spaces from a string
    void eatspaces(char* str)
    {
        int i = 0;
        int j = 0;
    
        while ((*(str + i) = *(str + j++)) != '\0')
            if (*(str+i) != ' ')
                i++;
        return;
    }
    
    // Function to evaluate an arithmetic expression
    int expr(char* str)
    {
        int value = 0;
        int index = 0;
    
        value = number(str, index);
    
        for (;;)
        {
            switch (*(str + index++))
            {
                case '\0':
                    return value;
                case '+':
                    value += number(str, index);
                    break;
                case '-':
                    value -= number(str, index);
                    break;
                default:
                    cout << endl
                         << "Arrrgh!*#!! There's an error"
                         << endl;
                    exit(1);
            }
        }
    }
    
    // Function to recognize a number in a string
    int number(char* str, int& index)
    {
        int value = 0;
        while(isdigit(*(str + index)))
            value = 10*value + (*(str + index++) - '0');
        return value;
    }