Topical Information

The purpose of this quiz is to give you a chance to focus your knowledge of C-strings in C++.

Quiz Information

Questions

1. All C-strings end in what character? Is this character in the last array position?

   
       The '\0' character ends all C-strings.  It is also known as the null
       character.
   
       It is not necessarily in the last array position.  It immediately follows
       the last char of the user's data.
   
   

2. The C-string library contains the functions _____, _____, and _____ to replace the operations =, +=, and (<,>,<=,>=,==,!=) respectively.

   1. strcmp, strlen, strcpy NO
   2. strcpy, strlen, strcmp NO
   3. strcmp, strcpy, strcat NO
   4. strcat, strcpy, strcmp NO
   5. strcpy, strcat, strcmp YES

3.  

   TRUE ✗		FALSE ✓		We typically process C-strings one element at a time like all other arrays (for input, output, assignment, etc.).
   TRUE ✗		FALSE ✓		There is no need to protect C-strings from overflow on input as we did with other arrays.
   TRUE ✓		FALSE ✗		When passing a C-string to a function, we normally don't pass the length of the array/data.
   TRUE ✗		FALSE ✓		Functions which process C-string arguments typically call strlen and then use a for loop to process the elements.

4. An array of C-strings is a _____ dimensional structure. Access using _____ indices arrives at a single character within a single string. Access using _____ index(es) arrives at a single string. Using no indices refers to _____.

   1. two, two, one, a character NO
   2. two, three, four, five NO
   3. two, two, one, the whole array YES
   4. 3, 2, 1, 0 NO
   5. three, three, two, the entire array NO

5. To protect assignment from overflow, the cstring library provides another version of the strcpy function. This new version has a(n) letter n in its name and a third argument which specifies a maximum number of characters to copy. This version will copy characters from the source to destination C-string until either the null character is copied or it copies the maximum number of characters.

   There is, in general, no guarantee that a null character is stored in the result array. To alleviate this situation, it is normal for a programmer to store one him/herself after a call to this function. (If they didn't, after all, their array would cease to be a C-string!!!)

6. Draw two pictures of an array of C-strings. One should be logical, the other more realistic. (Show the array containing contents such as: "Estelle", "Yrda", "Sue", "John", "Vong", "Dmitry", "Ng", "George".)

   
       Logical:                 Realistic:
       +=========+              +====+====+====+====+====+====+====+====+
     0 | Estelle |            0 | E  | s  | t  | e  | l  | l  | e  | \0 |
       +=========+              +====+====+====+====+====+====+====+====+
     1 | Yrda    |            1 | Y  | r  | d  | a  | \0 |    |    |    |
       +=========+              +====+====+====+====+====+====+====+====+
     2 | Sue     |            2 | S  | u  | e  | \0 |    |    |    |    |
       +=========+              +====+====+====+====+====+====+====+====+
     3 | John    |            3 | J  | o  | h  | n  | \0 |    |    |    |
       +=========+              +====+====+====+====+====+====+====+====+
     4 | Vong    |            4 | V  | o  | n  | g  | \0 |    |    |    |
       +=========+              +====+====+====+====+====+====+====+====+
     5 | Dmitry  |            5 | D  | m  | i  | t  | r  | y  | \0 |    |
       +=========+              +====+====+====+====+====+====+====+====+
     6 | Ng      |            6 | N  | g  | \0 |    |    |    |    |    |
       +=========+              +====+====+====+====+====+====+====+====+
     7 | George  |            7 | G  | e  | o  | r  | g  | e  | \0 |    |
       +=========+              +====+====+====+====+====+====+====+====+
   
   

7. Write a function which can change a C-string to all uppercase.

   
       void toupper(char s[])
       {
           size_t c{0};
           while ( s[c] != '\0' )
           {
               s[c] = static_cast<char>(toupper(s[c]));
           }
           return;
       }
   
   

8. Code the declaration of the array you drew above. Use your function from above to uppercase the contents of this array. (This code needn't be a whole program. A fragment will do.)

   
       const size_t MAX_NAME_LENGTH{8};
       const size_t MAX_NAMES{8};
       char names[MAX_NAMES][MAX_NAME_LENGTH] = { "Estelle", "Yrda", "Sue",
                                                  "John", "Vong", "Dmitry",
                                                  "Ng", "George" };
       size_t num_names = 8;
   
       for (size_t n = 0; n < num_names; ++n)
       {
           toupper(names[n]);
       }
   
   

9. The following function is terribly program specific:

       double input(void)
       {
           double pay;
           cout << "Enter your pay rate:  ";
           cin >> pay;
           return pay;
       }
   

   To fix it, we'd normally do something like this:

       // caller must prompt before calling us!!!
       double input(void)
       {
           double x;
           cin >> x;
           return x;
       }
   

   But with C-strings, we can now leave the prompt in the function and still have the function completely generic. Show how this can be done:

       double input(const char prompt[])
       {
           double x;
           cout << prompt;
           cin >> x;
           return x;
       }
   

10.  

    TRUE ✓		FALSE ✗		Having a function take C-string arguments can extend its usefulness to many new situations.
    TRUE ✓		FALSE ✗		Such C-string arguments are often 'pass-by-value' (which means they must be modified with the keyword const).
    TRUE ✓		FALSE ✗		The actual arguments passed to these functions can be either real arrays or literal C-strings.