If we imagine that the operations of are interactive user commands to manipulate text files, we readily see that they are definitely too limited. The main shortcoming is the fact that the user has no way to name files. It is possible only to build new files and then operate on them. Augment the previous specification to include a naming facility. lbe user must be able to give identifiers to files when creating them and use an identifier to specify the file to which an operation must be applied. You may consider the name, or identifier, of a file as different from the previous variables f,, fl, and 12 of sort Text. In other words, the name should be an attribute of a file, uniquely identifying it.