is it possible to implement Check in Check out on Sharepoint List Items?
Check-in/ Check-out is only available for document libraries. The physical check in/out process is done on the SPFile (document) and not the list item.
List items can be tracked using versioning.
sharepoint does not allow entry of values concurrently, meaning if you are modyfying list item 1 and user 2 also trys to do it, only after user 1 changes are submited user 2 can add his new value and in this case user 2 will get error, once user 1 done with his changes, user 2 will be allowed to change the list item.
so when user 1 changes list item 1, its locked for user 2 or any other user trying to change the value of list item 1 and gives an error.