Design+Your+Own+Program+(Conditional+Loops)

Task
Can you come up with your own program which:
 * uses a conditional loop

Design

 * Write down the inputs, processes and outputs of your program
 * Write down the names of any variables you will use
 * Write down the algorithm

Development

 * Write the program
 * Produce testing for the program
 * Produce a short user guide for your program
 * Produce a short technical guide for your program