Lens without A/M switch, still auto focus?

[jcs401]

i am looking at a lens for my Nikon d7100z. The seller says it doesn't have a A/M switch to go between manual and auto. Question is, if s lens doesn't have that switch does it automatically make it Manuel focus only??

 

[jaomul]

Some older lenses don't have af switch, you use the one on your body, lens is af by cameras inbuilt motor on Nikon cameras that have it. D7100 is capable, don't know bout this particular lens though