A pathname is a very descriptive way of telling an application the route to a document, but /PERSONNEL/SALES/JONES requires a lot of typing. Fortunately, there's a shortcut. You can set a prefix. A prefix is the first part of a pathname. It can be just the disk name (/PERSONNEL,) or it can be the disk name and the subdirectory name (/PERSONNEL/SALES). Once you've set the prefix, you don't have to type the whole pathname. You just type the document name (for example, JONES), and the application tacks the disk name and subdirectory name onto the front of what you type.
Setting a prefix allows you to work with different documents in the same subdirectory more conveniently. You can save or load any document in that subdirectory by typing just the document name, not the whole pathname. When you want to work with a document in a different subdirectory, you can either change the prefix or override the current prefix by typing the complete pathname of the document.
The application you're using will tell you how to set a prefix.
To make it even more challenging, some applications shorted the question to: S? D? (S stands for slot; D stands for Drive.)
If any application asks for a slot number and a drive number when you choose the Save command, it's asking which slot contains the disk drive controller card for the drive you want to save to, and whether that drive is attached to the drive 1 connector or the drive 2 connector on the controller card. (A disk drive controller card can control up to two disk drives.) If your disk drive is connected to your computer through a disk drive controller card the answer is straightforward. (Even if you can't remember which slot your controller card is in and which drive is attached to the drive 1 connector on the card, you can always remove the cover from your Apple IIGS and have a look.)
Saving a document