## How a Hard Drive Works

< Nick Parlante's home

Here's a 6 minute video which shows how a hard drive works to store 0's and 1's. There's a big version for in-class projection or whatever, and there's a smaller version below. browser does not support html5 video

The video file hard-drive.webm (you can download it if you like) is encoded in WebM which is free and open video standard supported by Firefox and Chrome out of the box.

Here's the smaller version hard-drive-small.webm: browser does not support html5 video

How a hard drive works:

- When you save a document, it gets written somewhere "non-volatile" that keeps its state even when the power is off. How does that work for a hard drive?
- The hard drive contains a spinning platter with a thin magnetic coating
- A "head" moves over the platter, writing 0's and 1's as tiny areas of magnetic North or South on the platter
- To read the data back, the head goes to the same spot, notices the North and South spots flying by, and so deduces the stored 0's and 1's
- A Modern hard drive can store well over a trillion 0/1 bits per platter, so the individual North/South spots are quite small
- "Flash" storage is made with chips (no moving parts) and is gradually replacing spinning hard drives like this. Flash chips are what's inside camera SDHC memory cards and USB storage keys.

These videos are released under the CC Attribution Sharealike 3.0 license