Regardless of their type, most fields are empty when you create a new record. Often, but not always, that's what you want—a completely blank slate into which you can type all the information pertinent to a record. But auto-enter options also put data into fields for you, saving time and reducing human error. Auto-enter options can also create things like serial numbers for a primary key (Keys) or store data about your records (Figure 6-2).
If you don't see any options in the Fields tab of your Manage Database window, click the Options/Comments column heading. That toggles it between showing comments and showing options.
On the Options for Field dialog box's Auto-Enter tab, the first two auto-enter options (creation values and modification values) let you create and maintain metadata. Many developers find these fields so useful for peeking behind the scenes that they create primary key fields and the four metadata fields shown in Figure 6-2 in each table before they create any other fields.
Information about records, as opposed to information about the entities you base your tables on (Modeling Your Database) is called metadata. Metadata helps you do basic forensics on your database. For example, if there's a question about an Invoice, you can see at a glance who created it, and then ask the person to solve the mystery. Plus, when data entry folks know you're tracking this kind of metadata, they may start being more careful, since they know you can track their mistakes back to them.
Figure 6-2. Top: This layout shows four auto-enter fields that store information about who creates and/or modifies each record and when they do so. Bottom: The Manage Database window's field...