The way we use technology, as well as the technology itself, has changed significantly over the last few years.

There used to be two main camps when it came to technology: PC and Mac. These were built around the two competing computers systems, Microsoft's Windows PC operating system and Apple's Mac operating system. Software was written specifically for each of these systems, so you couldn't use PC software on a Mac or Mac software on a PC.

When you bought a computer, you pretty much bought into one of these two types of computers. The PCs and Apple battled it out for years, with PC garnering more than 90 percent of the market and Apple never getting out of single digits.

Now, however, things have completely changed. With the introduction of the iPhone and the iPad, Apple has soared in popularity. Other large companies have become technology powerhouses. Google, with its Android operating system, and Amazon have both entered the fray, while Microsoft is struggling to keep up.

Previously, we were only talking about computers, but now we are talking about smart phones, tablets, and cloud computing. We are talking about entire ecosystems. The choices are mind-boggling. And each of the above mentioned companies is trying to get you to buy into their ecosystem.

Right now, Apple has the largest ecosystem - I call it an ecosystem because it is an entire network or environment where one thing is dependent on another.

Apple's iPhone and iPads run on the iOS operating system. These devices run apps, which are like mini software programs that are purchased from the iTunes App store. There are currently more than 500,000 in Apple's App store. Some are free, but many are sold for a fee. These can only be used on Apple devices.

If you switch to a Google Android phone or tablet, you cannot use the Apple products that you may have already purchased. You have to repurchase them from the Android Marketplace, which has apps similar to those found in the Apple iTunes store.

This ecosystem also extends to storage and services in the cloud (think Internet). Apple has announced a cloud service called iCloud that lets you store information on Apple's servers and access it from any Internet-connected device.

Amazon, Microsoft and Google also have cloud storage systems available. Since many of Microsoft's followers use Microsoft Office, Google has also developed a set of programs that are the equivalent of Microsoft Office programs, but that can be stored in the cloud and used from any Internet-connected device.

These companies make money from their hardware and their app sales. They give you a basic amount of cloud storage for free, but if you need more storage, there is a charge. You can see why so many companies are battling for supremacy of their ecosystem. It is very profitable.

Each of the current ecosystems is expanding. Apple not only has the software in its app store, but it also has the hardware in their iPhone, iPad devices and Mac computers.

Apple recently announced its new cloud storage system and an app store for its Mac computers. Its new Lion operating system, which is used for its Mac computers, is so similar to the iOS operating system that you have to wonder just how soon the Mac computer and the Apple iPhone and iPads will share an operating system. When that happens, they will have added another component to Apple's ecosystem.

Microsoft is a slightly different story. It doesn't manufacture smart phones or tablets, but it has a new mobile operating system called Windows Phone 7, which runs on hardware from other manufacturers. Microsoft has an App Marketplace like Apple and Google. It also has cloud storage.

The phones that run the Microsoft operating system shine at running Microsoft office programs such as Word and Excel. This is a part of its ecosystem. I expect that when Microsoft comes out with Windows 8, it will also be able to run on tablets, so we will soon see tablets running Microsoft software and apps.

Amazon has developed its own app store filled with Android apps. It also has a cloud storage system called Amazon Cloud Drive. It is already into the hardware business with its Kindle e-reader, and I expect that it will soon release a tablet to compete with the Apple iPad.

BlackBerry and HP have both entered this competition with operating systems, hardware and app stores of their own.

It's not that you cannot mix products. For instance, my husband has an Android phone, while we also own an iPad. He obviously can use both, but to do so, he had to learn two different operating systems.

On top of that, if he wants to have a certain app on both his phone and our tablet, we may have to purchase it twice, buying a copy for his phone from the Android Marketplace and buying a copy for our tablet from the iTunes store. So not only is it easier to stay within one ecosystem, it is also more economical.

Knowing about these ecosystems may make purchasing a tablet or a new smart phone a little more complicated. Besides assessing the qualities of the hardware, you also have to stop and think about the ecosystem you are buying into.

Yet, the number of large companies involved in this rivalry and the constant changes, additions and improvements they make to their lineups makes this a very exciting time in the history of technology.

Sandy Berger welcomes your questions and comments on today's column. She can be reached at sandy@compukiss.com.