Our entire design up to this point has been centered around a form that only appends data to a file; adding read and update capabilities is a fundamental change that will touch nearly every portion of the application. It may seem like a daunting task, but by taking it one component at a time, we'll see that the changes are not so overwhelming.
The first thing we should do is update our documentation, starting with the Requirements section:
The program must: * Provide a UI for reading, updating, and appending data to the CSV file * ...
And, of course, also update the part that is not required that follows:
The program does not need to: * Allow deletion of data.
Now, it's a simple matter of making the code match with the documentation.