Why do hard drives need formatting?

How would you answer this question without getting into technical details? How would you explain why do we need to format a hard drive before we can write data on it to a person who has just started using computers?

I’ve been trying to come up with a simple explanation for years! It only recently struck me that the formatting procedure can be easily illustrated.

All you need to unwrap the mystery of the great secret behind the hard drive formatting is a piece of paper.

This is a standard A4 sheet of paper and we want to write something on with a pen. But we can’t for obvious reasons — it’s crumpled up.

Same with the unformatted hard drive: it can not be used to write data because there is no space to write on.

Formatting procedure for a hard drive is similar to unwrapping of our sheet of paper. The surface of the hard drive eventually becomes available for writing.

When the sheet unfolded and straightened on the table it is suitable for writing with a pen. When the hard drive is formatted, it can be used to store data.

This explanation works well especially with my elderly co-workers. Linking new technology with something they can relate to (like pen and paper) makes it much easier for them to understand.