It was driving me insane. One of my cameras wasn't saving the day, date and other settings. I'd have to reenter them every time I powered up the camera, only to have them disappear when I turned the camera off.
I consulted the internet for the solution, and discovered my camera has a little button battery inside that preserved the memory. Easy access. I saw the battery type and number and headed for the store.
CVS and Walmart had at least a dozen sizes of button batteries, but not the one I needed. Radio Shack, how I miss you!
I went home and did what I should have done in the first place-- ordered the battery on-line.
It's one of the reasons why brick and mortar retailers are failing. I didn't expect CVS and Walmart to have every type of battery ever made. Specialty stores have just about disappeared.
Face it. It's an internet world.