San Francisco - There isn't one thing that jumps out with Apple's new Mac operating system, known as Mavericks - and that's a good thing.

Mavericks has plenty of modest refinements that add up to a system well worth the upgrade - even if Apple weren't giving it away for free.

Many years ago, Web surfing changed dramatically when the Opera browser offered a way to open multiple Web pages in tabs instead of separate windows that cluttered the computer desktop. Most browsers soon followed.

That concept now comes to file management as part of Mavericks, which Apple released Tuesday for new Macs and older ones running Snow Leopard, Lion or Mountain Lion. You can now use tabs rather than separate windows for various folders, disks and networked servers.

The change may seem cosmetic, but it saves time. As I opened a file here and move a file there in previous versions of the Mac OS, I could easily have a half-dozen or more windows open. If I closed them, I'd have to go through the trouble of finding those folders and drives again later. Instead, I resigned to the clutter and the inefficiencies that came with it.

Tabs mean I no longer have to accept that clutter. All the tabs are neatly organized at the top of a single window. I can access files and move them around more easily.

To further assist with file management, Mavericks lets you assign one or more tags to files. It's similar to the approach Google's Gmail uses to organize email.

I've been trying to go paperless by scanning or requesting bills and receipts electronically, but they've been scattered in more than 100 folders and subfolders.

The problem is that an individual file might belong in a number of folders. A receipt for a museum membership might go under "receipts," "museum," "charity," "taxes" or in a folder for the credit card I used. With tags, I can label the file with all five and find it more easily come tax time - or audit.

It doesn't matter anymore what folder I put it in. Searching by the tag will automatically pull the relevant file up.

Mavericks also has features that reflect a world in which people use multiple devices.

You can access your tags when you use another Mavericks computer, though not iOS devices such as iPhones and iPads yet. If you're sending a document using an Apple app, tags get stripped to preserve privacy.

Through Apple's iCloud storage service, the company's Safari browser already syncs bookmarks across Mac and iOS devices such as iPhones and iPads.

Stored passwords are now shared as well, along with credit card information. If you enter a credit card to buy a Miley Cyrus CD on a Mavericks Mac, you don't need to re-enter that information to buy earplugs from a different vendor, even when using an iPad. Apple says passwords and credit card information are encrypted for security.

And because you don't need to remember passwords, Safari can recommend hard-to-guess ones such as "Zsu-S5f-Lr7-gG4" to thwart hackers. That sure beats "password" as a password.

Apple e-books also sync. Mavericks introduces an iBooks app for the Mac, so you're no longer limited to iPhones and iPads. You can start a book on an iPhone and pick up where you left off on the Mac. Any highlights and notes transfer over. Bonus: Copy a passage into any app, and Mavericks automatically adds a citation.

Back to Safari, a new Sidebar offers quick access to bookmarks, sites marked for offline viewing and suggestions from people you follow on Twitter or LinkedIn. Unfortunately, Facebook links aren't part of that. A continuous scrolling feature automatically grabs the next site on your list when you get to the bottom of one.

Apple's much-maligned Maps app comes to the Mac. Last year, that app deposed Google Maps as the primary mapping app on iPhones, only to lead many people astray with mismarked landmarks and faulty directions.

The mobile app has gotten better, and the Mac version shares many of its attributes. You don't get turn-by-turn voice guidance on the Mac, but you can send results to your iPhone with two clicks. It's much easier to plan a trip using a real keyboard.

One peeve: Voice assistance on the phone seems to work only if you send just the destination. If you look up full directions with your planned starting point and send that, you'll have to flip through screens of directions manually, as I learned the hard way leaving San Francisco's airport.

Apple's mapping service also doesn't work on regular browsers, so you need an app on an Apple product - not Windows or Android. And it lacks transit directions.

Apple does integrate the service with its other apps, something it can do by building a stand-alone app. Click on an address in a Mail message for a small map within the app. You can then add the address to the Contacts app or pull up the full map in Maps.

And when you fill out a Calendar entry with an address, Apple uses its mapping service to calculate and block out travel time from the previous appointment. It also shows you a small map and the weather.

The Calendar app, meanwhile, is easier to read. Weeks no longer have to start on the same day each week, usually Sunday. Months don't have to begin on the first. You can view the last two weeks of one month and the first two weeks of the next on one screen, for instance.

Mavericks also offers easier ways to reply to chats and emails when notifications pop up on the side. I did have trouble when a friend and I sent each other streams of chats at once, without waiting for a reply. I can reply with only one line without returning to the chat app. And if another chat comes in as I'm replying, I see only the first message in the reply box.

But this and other gripes are rather minor.

Mavericks offers much more you won't see, but might feel. That includes better power and memory management. There are also improvements when working with multiple monitors.

Mavericks doesn't offer as abrupt a change as iOS did when it moved to version 7 this fall. And it's certainly not as revolutionary as Microsoft's transition to Windows 7 and a tablet-like format last year. But Mavericks goes far in extending an already powerful operating system for desktops and laptops, without taking away the aspects that makes it easy to use.

And by offering it for free, Apple is following the model it has adopted for iPhones and iPads: Make money on devices, and keep customers happy with the latest software innovations.

Just remember to back up your files before downloading and installing the update through the Mac's app store.