CD-ROM and Hard Drive

The CD-ROM is a storage device, not an input/output deivce. It has pits in it that helps it save information in it. There is a laser inside the CD player which would bounce off the shiny surface of the CD. If there is a pit, it would be read as 1. If there is no pit, it would be read as 0. So, in the end it's still binary. There are 3 layers in the CD: a shiny layer, a platic layer, and some metal inside. Devices such as CD's and DVD's are called optical media or optical storage. There are about 700 mb in a CD and 4.7 to 8 gb in a DVD. If you scratch a CD, it would defuse the light. To fill in the scratch, rub toothpaste or wax across it.

Unlike the CD, a hard drive isn't an optical device. It is a magnetical media. A magnet has North or South, and this could be read as on or off, just like in binary. 8 magnets in a hard drive is 1 bit. Hard drive is a metallic platter that has millions of magnets in it. Another magnet can damage your hard drive.

*Thermal compound is like a glue and it can prevent the CPU from turning too hot along with the fan. If the CPU becomes too hot, your computer would shut down.

*There's a battery in the motherboard makes the BIOS work. If you pull it out, and place it back on, all the settings in the BIOS would reset.