MOUNTAIN VIEW — Unless you were hiding under a rock for most of the day yesterday, you're aware by now that Google held a press event at which the search giant pulled back the curtain on ChromeOS, the OS that's really a browser (and is based on the browser that's really an OS). The search giant announced that it is open-sourcing the OS, and described in detail much of its nature and function.

In this article, we'll recap only a few of the highlights of the announcement, because the news has been covered exhaustively elsewhere. Our main focus here is to provide some analysis and context, and to think about what ChromeOS means.

The highlights

What Google unveiled in detail is actually more than just an OS. ChromeOS presumes a particular hardware platform—exclusively flash for storage, custom firmware, and a limited, Google-approved set of system and peripheral devices that the OS will recognize and use. This being the case, this article will refer to a "ChromeOS portable," because to think in terms of a "netbook that runs ChromeOS" is a mistake, for reasons discussed later.

The custom firmware integrates some of the functions of a boot loader, so it's a bit more robust than a traditional BIOS. During the seven-second boot time, the firmware loads a series of kernel modules, all of which are signed; if the signature check fails at any point in boot-up, the machine will prompt the user for a reboot, after which a clean version of the OS is downloaded and the entire device is essentially re-imaged.

Once you get past the custom firmware layer that lives on the "hardware" side of the portable, ChromeOS proper is essentially a version of the Chrome browser that runs right on the hardware, with as little as possible in the way of an intervening OS stack. Every "application" is just a webpage, which means that users don't install binaries, ever, for any reason. "We run completely inside the browser model," said Sundar Pichai, vice president of product management at Google when describing user application execution.

Each application in ChromeOS lives in a browser tab

The OS itself lives on a read-only partition that's not accessible to user-space processes. The fact that the OS is stateless is a major security advantage, since it's that much harder for malicious code to hijack any part of it. Also important is the fact that the user processes themselves are all sandboxed, and any user data that's locally cached is encrypted by default.

The OS will support only a limited number of Google-blessed devices and peripherals, which is Google's way of ensuring reliability and security. Users who buy a ChromeOS portable will have to buy it for what it is, a cloud client that's closer in many ways to a smartphone than it is to a netbook.

Speed and gaming

Google has promised that ChromeOS will provide an even faster Internet experience than the Chrome browser, and it's not hard to imagine how it will deliver on that. Because Google owns the TCP/IP stack in ChromeOS, the company can optimize it for Internet HTTP traffic: very high numbers of simultaneous connections and high latencies. Thus Google can make tradeoffs down in the networking stack that give a better user experience on ChromeOS, without worrying about how the OS will perform on a LAN with different file protocols and such.

As for the device's potential for gaming, it's certainly better than you think. The ChromeOS engineering director, Matthew Papakipos, is the former Director of Architecture at NVIDIA, and he came to Google as part of the search giant's purchase of Peakstream, a "GPGPU" middleware company that Papakipos founded. Papakipos was one of the principals behind Google's recently announced O3D API. The O3D API essentially lets Javascript Web apps use a client's GPU hardware for 3D acceleration, which means that you can run in-browser 3D scenes at full speed. While you won't be playing Far Cry on a ChromeOS portable any time soon, it should be possible to do some interesting virtual world type applications and casual games eventually.

Death to the file, long live the URL

In my comments above on how ChromeOS works, I described user data as "locally cached"—with ChromeOS, all user data lives in the cloud. A ChromeOS device presumes that the canonical version of your data is the cloud version, so it caches this data locally for faster access, and when a user modifies it, the changes are invisibly written back out to the network. What this means in practical terms is that, while ChromeOS has a filesystem of some sort, you'll never see it. I, for one, couldn't be more thrilled.

Longtime Ars readers may be familiar with my periodic rants about the increasing disutility of the "volume/directory/file" metaphor for modern networked machines. Saving files, copying them, syncing them—this is all pointless clerical work that I want my computer to do for me. ChromeOS officially nukes the "file" as a core user-facing OS abstraction. This is a huge victory for users everywhere, who can now interact with higher-level abstractions like contacts, geographic locations (variously described via Google Maps), documents, applications, and other more viable entities that don't digitally imitate the paper-based record keeping systems of a bygone era.

Of course, what Google has replaced the file with has problems of its own. I'm speaking of the URL, and let's hope that the URL is only a stopping-off point on the route to something better. URLs are long, unwieldy, not very user-friendly, and generally undesirable as a user-facing abstraction. Google must find a way to hide the URL permanently, so that users can locate networked resources using a less awful method than copying, pasting, or (God forbid) manually entering a lengthy and mostly nonsensical text string.

Note that it's still possible to browse a traditional filesystem with ChromeOS. If you plug a USB drive into the portable, ChromeOS opens a file browser tab that lets you look through the file tree. In the demo, Pichai clicked on a an Excel file that then opened in the Windows Live version of Excel. "Microsoft has written a killer app for ChromeOS," he snarked of Redmond's Live offerings, which will enable ChromeOS to natively open Office docs without translating them to Google Docs.