When we need to generate a letter of the alphabet, such as a word or name, we are looking for some way to keep the output random without actually having to use a random number generator.We can't use a random number generator because if we have a sequence of letters, we need them to be in alphabetical order.If we used a random number generator we would get a different sequence each time we ran the program.But we want it to be the same each time, so that it can be used for the same purpose, such as in a game or in a word puzzle.