Are all Pentax dslr lenses the same?

I have had a Pentax K100D for my birthday today. Whoop whoop, I was just wondering whether it has a specific lense that fits that camera or whether all Pentax lenses fit it. In fact can any lense fit it, like a canon or Nikon lense? Also what are the best accessories you would recommend to get for it that are cheap because I'm only starting off now but I hope to become professional over time.

Only Pentax-fit lenses will fit a Pentax camera. Some third party manufacturers also make lenses that fit Pentax cameras.

You might be able to buy an adapter to fit Nikon, Canon and other lenses, but they are expensive and usually reduce the quality. Just stick to buying Pentax lenses!

Older Pentax lenses will also fit but note you won't get autofocus or auto-aperture with these lenses. If you're happy to go manual, you can save money and get good glass this way. But if you're new to SLR photography, stick to modern Pentax lenses until you've got some experience.

Have fun!

Most professionals use Nikon and Canon cameras.

Why?

The professional industry is set up for those camera systems

* The best third party lenses are only made for Nikon and Canon cameras, the Tokina lenses
* Adobe Lightroom 3.6 only tethers to Nikon and Canon cameras
* Only Nikon and Canon have professional services for their users
* Both Nikon and Canon have over 60 different current lenses for their cameras.

Too bad you did not do more research before getting the nice gift.

As a beginning photographer, all you need is the camera, the lens that came with it and the user manual for about the first year or so. Accessories you really need may be a custom white balance tool and a computer monitor calibration tool before any thing else, including an external flash and tripod. Those will come later after you have mastered using the camera as you received it in the box