國立暨南國際大學 105 學年度第二學期 第一次期中考試卷

1. (10%) Determine whether the following code has syntax errors or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
   
   // Range of Values (P.45)
   // Overflow (P.125)
   #include <iostream>
   using std::cout;
   using std::endl;
   
   int main()
   {
       signed short n = 32767;
       n += 2;
       cout << n << endl;
   
       unsigned char c = 'w';
       c = c * 3;
       cout << c << endl;
       return 0;
   }
   
   
2. (10%) Determine whether the following code has syntax errors or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
   
   // Conditional Operator (P.103)
   #include <iostream>
   using std::cin;
   using std::cout;
   using std::endl;
   
   int main()
   {
       for (int i=0; i<10; i++)
           cout << (i%2 ? i : ++i) << endl;
       return 0;
   }
   
   
3. (10%) Determine whether the following code has syntax errors or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
   
   // Bitwise Operator (P.67)
   #include <iostream>
   using std::cout;
   using std::endl;
   
   int main()
   {
       unsigned char m = 0x4d;
       unsigned char n = 0x6e;
       cout << m << n << endl;
       cout << static_cast<char>(m & n) << endl;
       cout << static_cast<char>(m | n) << endl;
       cout << static_cast<int>(m ^ n) << endl;
       return 0;
   }
   
   
4. (10%) Determine whether the following code has syntax errors or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
   
   // continue (P.116) vs. break (P.115)
   #include <iostream>
   using std::cin;
   using std::cout;
   using std::endl;
   
   int main()
   {
       const int K=10;
       int m=0, n=0;
       int i, j;
   
       for (i=0; i<K; i++)
           for (j=0; j<K; j++)
           {
               if (i+j == K)
                   continue;
               ++m;
           }
   
       for (i=0; i<K; i++)
           for (j=0; j<K; j++)
           {
               if (i+j == K)
                   break;
               ++n;
           }
   
       cout << m << n << endl;
       return 0;
   }
   
   
5. (10%) Determine whether the following code has syntax errors or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
   
   // ASCII Code (P.42, P.95)
   #include <iostream>
   #include <cstring>
   using std::cin;
   using std::cout;
   using std::endl;
   
   int main()
   {
       char text[]="this is a string.";
       char *p = text;
       bool afterSpace = false;
       while (*p)
       {
           if (*p == ' ')
               afterSpace = true;
           else
           {
               if (afterSpace)
                   *p &= 0xDF;
               afterSpace = false;
           }
           ++p;
       }
       cout << text << endl;
       return 0;
   }
   
   
6. (10%) Determine whether the following code has syntax errors or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
   
   // switch (P.105)
   #include <iostream>
   #include <cstring>
   using std::cin;
   using std::cout;
   using std::endl;
   
   int main()
   {
       char msg[] = "SECRETMEETING";
       int even = 0, odd = 0;
       int i;
       for (i=0; i<strlen(msg); i++)
       {
           switch (msg[i] % 2)
           {
               case 0:
                   ++even;
               case 1:
                   ++odd;
           }
       }
       cout << "Even: " << even << endl
            << "Odd: "  << odd  << endl;
       return 0;
   }
   
   
7. (10%) Suppose you compile and run the following code on a 64-bit computer (e.g. STU.ipv6.club.tw).  What will be its output?
   
   // The sizeof Operator (P.154)
   #include <iostream>
   using std::cout;
   using std::endl;
   
   int main()
   {
       char strAry[] = "This is a string";
       char *aryPtr = strAry;
       short *shortPtr = (short*)strAry;
   
       cout << "[Line01] sizeof(strAry)=" << sizeof(strAry) << endl;
       cout << "[Line02] sizeof(aryPtr)=" << sizeof(aryPtr) << endl;
       cout << "[Line03] sizeof(*aryPtr)=" << sizeof(*aryPtr) << endl;
       cout << "[Line04] strAry=" << strAry << endl;
       cout << "[Line05] aryPtr=" << aryPtr << endl;
       cout << "[Line06] *aryPtr=" << *aryPtr << endl;
       cout << "[Line07] *aryPtr+1=" << *aryPtr+1 << endl;
       cout << "[Line08] *(aryPtr+1)=" << *(aryPtr+1) << endl;
       cout << "[Line09] sizeof(shortPtr)=" << sizeof(shortPtr) << endl;
       cout << "[Line10] sizeof(*shortPtr)=" << sizeof(*shortPtr) << endl;
   
       return 0;
   }
   

8. (10%) Determine whether the following code has syntax errors or
       not.  If it is correct, predict its output.  If it is
       incorrect, point out the
       mistake(s).
   
   // Letter Grouping
   #include <iostream>
   using std::cin;
   using std::cout;
   using std::endl;
   
   int main()
   {
       const int MAX_SIZE = 80;
       char plaintext[] = "It's easy to read this sentence";
       char buffer[MAX_SIZE];
       char* p = plaintext;
       char* p2 = buffer;
       while (*p)
           if ('A' <= *p & *p <= 'Z' || 'a' <= *p & *p <= 'z')   
               *p2++ = (*p++ & 0xDF);
           else
               p++;
       *p2 = '\0';
   
       p=buffer;
       while (*p)
       {
           cout << *p++;
           if ((p - buffer) % 5 == 0)
               cout << ' ';
       }
       cout << endl;
       return 0;
   }
   

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

   // Transposition Cipher
   #include <iostream>
   using std::cin;
   using std::cout;
   using std::endl;
   
   int main()
   {
       char cipher[] = "CFITSLINMEOVGECCEAERKOTTE";
       int i, j, p=0;
       char matrix[5][5];
       for (j=0; j<5; j++)
           for (i=4; i>=0; i--)
               matrix[i][j] = cipher[p++];
   
       for (i=0; i<5; i++)
           for (j=0; j<5; j++)
               cout << matrix[i][j];
       cout << endl;
       return 0;
   }
   

10. (10%) Suppose you compile and run the following code on a 64-bit computer.  Determine whether the following code has syntax errors or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
    // Pointers to Array of Characters (P.155)
    #include <iostream>
    using std::endl;
    using std::cout;
    
    int main()
    {
        const char* s[] = { "NCNU", "~/-\\^" };
        char c = s[1][2];
        const char* p = &s[1][2];
        cout << sizeof (s) << endl;
        cout << sizeof (s[1][2]) << endl;
        cout << c << endl;
        cout << *(++p) << endl;
        cout << p << endl;
        return 0;
    }