I recently received the following from Wayne R.: "I use RPG's %CHECK function to check if any characters are not valid. Is there something similar in CL?" RPG's %Check built-in, if you're not familiar with it, returns the first position in a variable that contains a character that is not in a list of valid characters. If, for instance, you had a variable with a value of 'cabbage', then comparing this to a list of valid values such as 'abc' would return a position value of 6. This is due to the sixth character (the "g") not being in the list of valid values ('abc'). If all characters in the variable are found in the valid character list, %Check returns a position value of 0. While CL currently does not have a built-in such as RPG's %Check, you will see it's not that difficult to create a CL command to provide this function for programming our IBM i—and in fact that's what we'll do in today's article.