On a hard disk: What is the surface made of? What makes the disk reusable, and not permanently scratched? How does that little hair read data so fast? How is the data stored? And I'm asking, not quizzing :good: Thanks.
I'm not sure what the actual platter is made of but its covered with very fine metal powdery type stuff i think which can be manipulated by the magnetic field created by the write head. The powdery stuff isn't permanently stuck to the platter, so it can be moved by the magnetism. So its reusable.
I believe the disks are some type of ferrous metal (iron-based). Unlike CD's hard drives operate on a magnetic medium. The read/write heads deal with polarity and to signify 0's and 1's by this. Gold is far too weak of a metal to be used on hard drive platters. It is used in electronics, but more for connectors as they tend to have good signals.
A disk is divided in platters, sectors and cylinders. The platter is round-shapped and is read by heads. Imagine the platter is a pie. The sectors are the different pieces of the pie. Also, on the platter itself are "circles", which line up with the other circles on the other platters. The circles that are aligned make a cylinder. Not sure if it's clear or not...probably not
Here, I made a high precision drawing with my paid version of Paint :good: The sector is the smallest unit. The platter is the whole thing. As for the cylinders, imgaine several platters are piled up. A cylinder is formed of all the round sections that are ligned up.
Yeah, like Big B said, they are magnetic iron based metal disks! They are hella strong too, I couldnt snap a 40gig one with my bare hands by bending it!
CDs are optical devices. A laser shines on it and the laser bounces off were there are no bumps and the laser does not bounce off were there are bumps. The CD drive then reads where there are bumps and converts that to usable data. Hard drives are magnetic devices.
