Filing Cabinets

The basic concept behind a Hash Map is the same concept as a filing cabinet.

If you grew up in a doctor's office like I did this will make sense. If you didn't, look up what a filing cabinet looks like.

Basically, if you have folders for a bunch of people you can separate them into different cabinets.

You start by putting everyone in one cabinet. If you want to find someone's records, you look through everything in that cabinet until you find it.¹

Once you have enough records you separate your folders by something like the patient's last name. So you would have your A-M and N-Z cabinets.

Then when you want to find someone, you can quicky pick the right cabinet by looking at their last name.

If you got too many people in one cabinet you would then subdivide that cabinet further.

And this basic system can scale to thousands of names.