Let's ask Pierre Kerr, ac210@freenet.carleton.ca, how computer discs are made.

There are a few different kinds of computer discs (or disks) Noha. Let's see what there are. I've given you some samples.

The big one is an old 8 inch floppy disk. It's called floppy because it can bend a little bit. You shouldn't bend it too much but this one is not used anymore so you can do what you like with it. I have cut the end of the case off so you can slip out the shiny brown disk that's inside. That disk turns around very quickly when it's in the computer.

Floppy disks work because they can store information as very small magnetic signals. The brown plastic that makes the disk is the same material that is used in audio cassettes and video tapes.

There are other sizes of floppy disks. The most common one these days is a 3 1/2 inch disk and it's still a floppy disk but is in a hard plastic shell. I've given you two of those glued to a piece of cardboard so you can see inside.

There are also hard disks. These are normally inside a computer so you can't see them. They still use the same brown material to store the magnetic information but it is on a hard surface such as aluminium. I have given you an old broken hard drive to look at. Notice how the brown disk spins. When it is turned on it will spin very quickly. When this is in a computer, you wouldn't be able to see the disk part at all.

The little arms are what is used to read and write information on the disk. They can move back and forth to different parts of the disk. The hard disk has the arms built right on the disk but the floppy disks use heads that are inside the computer's floppy disk drive. They work about the same way though.

Show the disks to the other students on your class and perhaps you would like to set them up on a table so everyone can see them. They're yours to keep.

Thanks for the question Noha.