Lenses for SLR and DSLR cameras

DSLRs became affordable around the mid-1990s, and have become extremely popular in recent years. Some manufacturers, for example Minolta, Canon and Nikon, chose to make their DSLRs 100% compatible with their existing SLR lenses in the beginning, allowing owners of new DSLRs to continue to use their existing lenses and get a longer lifespan from their investment. Others, for example Olympus, chose to create a completely new lens mount and series of lenses for their DSLRs. The Pentax SLR camera K-mount system is backward compatible to all previous lens generations from Pentax, including the latest digital SLRs like the K-3 and K-50. A Pentax K-mount lens from the early 70s can be used on the newest Pentax DSLR although it may not provide features that are included in newer lenses (e.g. autofocus). There are a few exceptions from the MZ and ZX series of Pentax film cameras that do not work with some of the older lenses.

Question: do all dslr lenses fit all dslr cameras
Answer: no