You don't have to be a technophile to know a few things about compatibility. VHS tapes don't play on a laptop, iPhone apps don't run on your microwave and a CD won't play in a toaster.
Most people probably assume you also can't use Mac or Windows programs on an iPad. The iPad, the world's most popular tablet, runs its own flavor of software.
Which is a shame, really. All kinds of programs would be useful to have on your lovely, lightweight tablet: Quicken. Photoshop. iTunes. The full-blown Word, Excel, PowerPoint. AutoCAD.
I'm pleased to report that such a thing is possible, thanks to a remarkable new app, Parallels Access. Parallels, the company, has a good deal of experience running incompatible programs on popular computers; its best-known product lets you run Windows on a Mac.
Access is not some miracle adapter that runs Mac and PC programs on the iPad itself. Instead, it's a glorified porthole into the screen of a real Mac or PC back at your home or office. You see everything on your distant computer remotely; you can even click, type and drag in the programs there, even listen to audio and watch videos. The iPad becomes like a detached touch screen for a Mac or PC that's thousands of miles away.
It's not just about running desktop software, either. This setup also means you can access the far greater storage and horsepower of your computer. And you can work with files you left behind. The one catch: It requires an Internet connection. Access works over slower connections -- like 3G cellular -- but barely. You may encounter severe lags and blotchiness.
To make this come to pass, you set up Access on both ends. You install one app on your iPad, and another on your Mac or PC (Mac OS X 10.8 or later, Windows 7 or later). You also create a free account at Parallels.com.
From now on, whenever you want to operate your Mac or PC by remote control, you open the Access app on the iPad. You tap the picture of the computer whose brain you want to enter; there's nothing to stop you from setting up two, or 12, or hundreds of Macs and Windows machines to listen for the iPad's call.
When you first connect, you see a launcher: an iPad-style screen full of icons. In this case, they represent your Mac or PC programs. Tap one to open it. This launchpad starts out showing only the icons of your most frequently used Mac or Windows programs, but you can tap a "+" button to add other icons.
Parallels Access is not the first product that lets you access your Mac or PC remotely. There are many iPad apps that do that, bearing names like VNC Viewer and Real VNC. They cost $10 or $20. Corporate tech workers adore them. From wherever they happen to be, they can see, operate and troubleshoot the computer back at headquarters from the screen of a single iPad, without having to put on pants and drive to the office.
But Parallels Access is superior, for many reasons.
First, VNC apps are extremely technical to set up. Here's an excerpt from the dozens of setup steps for Real VNC, one of the best reviewed apps: "By default, VNC Server listens on port 5900. You can listen on a new port, providing no other service or program is doing so. Note you will have to specify the new port when connecting, and you may need to reconfigure firewalls and routers." O.K. then!
Parallels Access requires no fiddling with routers, firewalls or port numbers. You fill in your Parallels name and password, and boom: the connection is made, with 256-bit AES encryption (translation: "very securely").
Second, VNC apps display the entire computer's screen on the iPad. Icons, toolbars and buttons wind up about the size of subatomic particles.
Access, on the other hand, "appifies" the Mac or Windows program; the document you're editing fills the screen. All the iPad touch-screen gestures work to operate the remote program, too -- drag with one finger to scroll, for example. Tap to "click the mouse." Tap with two fingers to "right-click." Pinch or spread two fingers to zoom out or in. No matter what the Mac or PC program is, it suddenly behaves as if it is an iPad app.
Access is filled with additional touches that VNC-type programs generally lack, which further adapt mouse-and-keyboard software to a touch screen.
For example, when you need to see some tiny interface item, you can hold your finger down momentarily. Access displays the familiar iPad loupe -- a magnified circle -- that lets you tap or drag with greater precision. That magnified area also makes it easy to see when your cursor shape has changed, as it often does in programs like Excel and Photoshop.
You can highlight, copy and paste text and graphics using the familiar iPad conventions; for example, once you've selected some words, the usual iPad row of black buttons (Cut, Copy, Select All and so on) shows up. When you need a keyboard, you can tap a button on the unobtrusive, hidable Access toolbar, and a big on-screen keyboard appears, with all the traditional Mac or Windows keys (Esc, Tab, Ctrl, Alt, F1, Home, End, arrow keys and so on).
The iPad's text-entry features still work, even though you're typing into a program on the other side of the world. For example, you can speak to dictate, or you can use the iPad's non-English keyboards, or even the iPad's little character-drawing sketch pad for Chinese character recognition.
In short, Access does a lot more than just blast your computer's screen onto the iPad's. It truly does "appify" your computer's programs. It creates a smooth, logical hybrid of iPad and "real" computer, in a way that the VNC apps do not. It works amazingly well.
I do, however, have my beefs with Access.
First, your Mac or PC has to remain on and awake all the time. If it ever goes to sleep, your iPad's "call" will go unanswered. From an environmental and cost standpoint, that's not a great situation. You have the same problem with VNC apps, of course.
You should know, too, that when your iPad is connected, nobody at the other end can use the Mac or PC. The iPad takes over its soul. Its screen shows exactly what the iPad does: a squat, rectangular, one-window image. (Or, if you worry about snoopers seeing what you're doing on your iPad, you can opt to have the Mac or PC screen go blank.)
The bigger concern, though, is the price: $80 a year. That's right: Access requires a subscription (after a 30-day trial).
The problem here isn't the $80. It's the "a year." Subscriptions make sense when a company provides you with some good or service month after month. Electricity, cable TV, Internet, magazines, fruit in a box. Fine.
Parallels says that it is providing a service -- your connection from iPad to computer goes through its secure servers. But those VNC apps cost a one-time $10 or $20. No, they're not as good, but they also don't saddle your life with yet another eternal subscription. $80 a year, forever, seems steep.
Otherwise, wow. Parallels Access is quick to set up, simple to understand, almost limitless in potential. It brings millions of full-powered, high-sophistication Mac and Windows programs to the screen of the humble iPad -- backed by the full speed, storage and memory of those Macs and Windows machines. If $80 a year seems worth it to you, then guess what? Another great wall of incompatibility has just fallen.
This article originally appeared in The New York Times.