Let's now combine some of the things we have learned so far and start building a maintenance app for the contacts we used throughout Chapters 5, Working with Series and Blocks, and Chapter 7, Working with Files. Our data store is a text file named contacts. Each line has the contact's name, the contact's address, and a telephone number, all fields separated by a semicolon (;).

Here's an example:

John Smith;123 Tomline Lane Forest Hills, NJ;555-1234
Paul Thompson;234 Georgetown Pl. Grove, AL;555-2345

Here is the application screen:

The names of our contacts are shown in the text-list face. When a name is selected, this contact's details appear in the fields in the panel on the right. A new contact can be filled in and added to the list. When the Save button is pressed, all contacts are saved to the contacts file.

Here is the code. By...