Topical Information

The purpose of this quiz is to give you a chance to focus your knowledge of simple file handling in C++.

Question Set Information

Questions

1. Before you can open a connection to a file stream, you must do three things:

   1. declare a vector of objects to store the file contents. NO
   2. get from the user the name of their file. YES
   3. #include the library fstream. YES
   4. declare either an ifstream or an ofstream variable to connect to the file with. YES
   5. declare a variable to count how many lines we've processed in the file. NO

2. Once you are ready, you'll need to do two things to make a connection to a user's file:

   1. clear the stream variable to make sure it is ready to use. NO
   2. convert the string filename variable to a c_str as you pass it to the file connecting method. NO
   3. pass your string filename to the file connecting method as is. YES
   4. use the connect method with respect to your stream variable. NO
   5. use the open method with respect to your stream variable. YES

3. When opening a file connection, make sure the stream connected successfully to the file by:

   1. clear the filename string inside the checking loop. NO
   2. checking for fail or !good or even just !. YES
   3. use >> instead of getline for the filename the second [and later] time[s]. NO
   4. clearing the stream variable after the checking loop is done. NO
   5. using close and clear inside the checking loop. YES

4. What functions/operations can you use to get data from an ifstream variable?

       
       >>, getline, peek, etc.
   
   

   What functions/operations can you use to put data into an ofstream variable?

   
       <<, setw, flush, etc.
   
   

5. What is the type of getline's first argument that it can be used to read from either cin or an ifstream variable?

       
       istream & is compatible with both the console stream
       cin and any ifstream variable.
         
   

   What type should you use to allow a function to 'display' to either cout or an ofstream variable?

   
       ostream & is compatible with both the console stream
       cout and any ofstream variable.
   
   

6. Show pseudocode for a good loop to read until the end of a file is reached.

   
       peeky read
       while ( ! eof )
       {
           read data
           process data
           peeky read
       }
   
       The peeky read should be a ws extraction when extracting data in the loop
       or an actual peek when getline is being used to gather data in the loop.
   
   

7. Show a good loop to open an input file the user specifies.

   
       prompt for and read file's name (getline)
       attempt to open file
       while ( ! file )
       {
           close/clear the ifstream
           print an error message
           prompt for and read file's name (getline)
           attempt to open file
       }
   
   

8. How does this get complicated when the file is an output file? What else can go wrong besides those things that happen with input files?

   
       Opening an output file automatically erases any content the file may
       contain.  This can be disastrous for the user!  To avoid this, we need
       to take advantage of the input file's ability to open an existing file
       but to fail when a file doesn't exist.
   
       To alleviate this issue, we can open the file name as an input file and,
       if successful, offer to the user to open it for appending instead of
       plain output.