enter code and give user a point

This requires a new module to be written to use the Userpoints API as a mechanism.

Other sites have done it by doing the scan outside of the Drupal web site, and then transferring a data file with transactions (user ID or email, and number of points, plus a description).

A custom module then reads the data file via cron and awards the points to the users on the site.

This is a project onto itself, so I can't "guide" you, beyond the 5-10 minutes answers.

There are lots of unknows here, and your problem at present is not the technology or (if), but rather requirements (what), then implementation (how):

You don't say how the scanner will interact with the web site, if at all.

What happens if users pass the bar codes to others? Will they be accepted or flagged as duplicate?

Will the site keep a list of unique bar codes and allow only one user per code? Where does this list come from? How large it is?

As you can see, this is not a simple question with a simple answer. Yes, Drupal and Userpoints can do anything, but the devil is in the details as they say.

agree that this is a completely separate project and shouldn't be part of the core userpoints, setting as "won't fix"

+1