CSCI 261 - Programming Concepts

The focus of this assignment is on one concept: how to read data from an "input file stream" or ifstream object.

Today's class discussed how data is often treated as "streams" of information that can be read a piece at a time. The files we will read in CSCI 261 are simple text files; for lab today, the simple text file contains a series of characters. Remember that whenever you work with a file stream as input, we call them ifstream objects.

There will always be four things you will do whenever working with an ifstream . Open the file, check for an error, read its data, and close the file. The typical pattern for this is as follows:

Remember, once you have an ifstream object (like myCatsAges shown above) you use it in a manner similar to using cin .

The cows have been kidnapped by aliens! The only clue to their whereabouts is a strange "ciphered" message, stored in the file secretMessage.txt. Fortunately, our in-house cryptanalysis expert, D. Cipher, has discovered the key:

"The key isn't very advanced, mmmkay? To decipher the message," she says, " you should take each character and replace all ~ (tilde) characters with a space, and shift all characters up by one, mmmkay?"

Your goal for this assignment is to create a program that reads the ciphered text file and then writes a deciphered version to a file called decipheredMessage.txt . For each character in the file, your program should implement the following replacement algorithm:

To see if your implementation works, you should be able to open the file decipheredMessage.txt and see the information about the missing cows.

Any input file needs to be placed at the project level, which should be the same directory as your main.cpp file. You should see both your input file AND main.cpp file in the same directory.

After you run your program, you will likely get an error saying the requested input file cannot be found. This is the same problem we initially had with our output files. CLion is looking in the wrong place. We need to tell CLion which folder to use.

To do so, we need to tell CLion where the files live. This can be found from going to Run > Edit Configurations. In the pop up window that appears, we want to set the "Working Directory" to be the path to the folder that our main.cpp file is located in. Hit Apply and OK, then rerun the program. You will now see the file created next to main.cpp.

In order to capture and replace whitespace characters, you will not use the >> operator with the input filestream. Instead, you will use the get() function like this:

This example assumes your ifstream is called secretMessage and you have a char variable declared that is called c .

Note that one requirement is to model the logic of the deciphering algorithm using a proper if/else-if/else construct. A switch statement could also be used.

Remember, cout and ofstream objects are sensitive to the datatype of the value to be printed or written to a file. Consider the following:

What is printed to the screen? The number 99. Why? Because a char plus an int yields an int , and then the int is "sent" to cout . To print the character c to the screen, you will need to use casting, like this:

Ahhh, much better.