An array would be a good way to store your questions, select them, and also mark whether a question has been used. Say you have 20 questions. Create an array with a width of 20 and a height of 2. Think of it as a grid with 20 columns (X dimension) and 2 rows (Y dimension). In the first row of each column, you put the text of a question. In the second row, you put a numeric marker, 0 for unused and 1 for used. Initially, all the markers would be set to 0. When a question is used, you have the program set its marker to 1. Then, if the random picker picks a question with a marker of 1, you tell it to pick again. It keeps trying until if finds a question with the marker still set to 0. Given the speed of modern computers, this will happen very fast, even if the program has to try again many times.