Apps often need to ask users questions during long operations like installation or file copying. Whenever possible, it's good to front-load these questions whenever possible. It's irritating to walk away from a process that the app says will take an hour, then come back an hour to discover the app's only 5% done because it's waiting for you to answer a simple Yes or No question.
I was reminded of this again during a hunt for a better file synchronization utility for Windows. For years I've used Second Copy by Centered Systems, which has been as a straightforward workhorse, but I thought I'd see what else is out there now.
As a rule, file synchronization tools have atrocious user interfaces. The people who really care about the fine points of synchronization or backup tend to focus on the technical challenges and ignore the greater challenge of presenting a simple user experience. These products typically have tabbed dialogs or wizards chock full of options that cover an enormous range of scenarios. Figuring out how to configure these options to get the product to do something basic often requires far more time than I'm willing to spend.
I've recently tried out a number of products, including ViceVersa by TGRMN Software. The UI in ViceVersa is only about average in terms of simplicity (in other words, not very simple), but they do offer an obvious and helpful mode that compares the contents of two file systems locations that are about to be synchronized. This lets you make sure you'll get the results you want. I thought the comparison mode was a nice touch, and after reviewing the results of such a comparison, went ahead and initiated a sync.
The sync ran for many hours, and restarted so many progress bars that I lost count. Each phase of the sync process provided an estimate of how long that phase would take, but as far as I could determine, that estimate was meaningless because I had no idea how many other phases were yet to come or long those phases would take. Because the file sync was tying up two machines, I effectively had no idea when I would regain use of either of them.
This is all par for the course in utility program UIs, but what was particularly irritating was coming back to the PC the next morning to find a dialog asking me to confirm that a given file should be overridden. This was quite disappointing. The application had earlier performed an exhaustive comparison of the files to be synchronized—for the very purpose of letting me confirm that I wanted to copy or delete the files as indicated.
If the application wanted to draw my attention to some particularly questionable operations, it already had essentially all the information it would need to ask me all of those questions up front. As far as I could tell, there was virtually nothing that the product would find out later during the file sync process that it didn't already know before the sync began. There could perhaps exist some cases where this wouldn't be the case (e.g., arising from files that changed while the operation is in place), but even then the product should have been able to take some reasonable default course of action—confirmed in advance if necessary.
The general point here is: when designing UI to support a long operation, consider whether any questions could potentially arise during the operation, and strive to move those questions to the point before the operation begins in earnest. Specifically, let the user know when they should be able to walk away and come back to find the process complete.
I recall one UI like this that came up a long time ago in Microsoft's first email product, Microsoft Mail. (Microsoft Mail, interestingly, was written for Macintosh computers and ran on AppleTalk networks.) During a certain operation, the product needed to have the user insert and remove a sequence of floppy disks. To its credit, the team took incredible pains to: a) order the disk insertions so as to minimize the number of times during the process that the user needed to remove one disk and insert another, and b) ensure that the longest disk operation took place last.
It's likely that no user ever perceived these refinements to the process, but I'm sure that some significant number of users were nevertheless saved the irritation of returning to their desk to discover that their computer was stuck halfway through, awaiting their return.