It occurred to me that most people (particularly those relatively poorly educated in the computer field) don’t know the basic functionality of web computer applications. Much of this also applies to applications which are not web hosted, but native to an operating system.

There are some functions done on computer which are unique and defy easy categorization, such as reconciling a checking account. They just don’t fit any box and are unique to the application you’re running. This essay is not about those screens. It’s about all the other functions which are more easily categorized.

In general, there are 5 types of screens you will run into in running an application:

1. Listing screens

   These generally list a table of values, like a check register. The items will be of like type, and the listing screen will list various characteristics about those items. A good example would be a check register. Each line in the register would be a transaction on that account, be it a check, deposit, draft or whatever. You’d see when the item occurred, how much it was for, who it was to/from, a balance, etc.

   These screens are meant to be informative and useful, and give you a general idea of what’s going on.

2. “Show” screens

   These, in contrast to listing screens, typically deal with a single item. You usually see all the aspects of this item, or at least all the aspects which would be of use to you as a user (not as a programmer). An example of this type of screen would be a “check” screen, where you’re looking at a single check from your checking account. You’d see the date, payee, amount, category, check number, etc. The key thing to understand about this type of screen is that it deals with just one item, unlike “listing” screens above.

3. Add screens

   In a screen like this, you’re adding an item to an existing collection of items. An example might be a checking account deposit screen. You’re filling out values for the date, amount, vendor or payee, etc. Most important, when you’re done, the item you’re giving values for on the screen will be added to a collection of like items somewhere inside your computer, like your checking account.

4. Delete screens

   In this type of screen, you’re looking at some sort of “show” screen, but you’re being asked if you want to delete the item. That’s about the simplicity of this screen– do you want the item gone or not?

5. Edit screens

   This screen shows you the particulars of an existing item, say a check, and allows you to change characteristics of the item, such as the date the check was written or the payee. When done, you will hit the appropriate button to signal you’re done with the edit, and the item with its changed detail will be filed. In theory, it will replace the item which was originally in you collection of like items (for example a check register).

In general, with few exceptions, most screens will be in one of these five categories. Screens may be labeled exactly as above, but no matter how they’re labeled, they’ll fall into these categories. There are few exceptions.

Even in more advanced, non-web applications, this division applies, though it may be less obvious. Take an application like Photoshop. Almost all the screens in Photoshop are edit screens. They allow you to change the color, size or contrast of an image, for example. But what they really are is various types of “edit” screens. Photo or image editing is a relatively complex process, so there are all kinds of ways to edit an image for different purposes. But in the case of a checking account edit screen, the edits you perform would be limited, because the item itself is far less complex than an image.

In using any screen, it’s useful to consider what type of “item” you’re dealing with, since the types of screen available have a lot to do with that item and its characteristics. Consider the types of items you might deal with on a day to day basis: sound recordings, photos and images, checks and deposits, song lists, phone numbers, appointments and reminders, etc.