Storage in Computers IO Magnetic disks A magnetic
- Slides: 8
Storage in Computers I/O • Magnetic disks: • A magnetic disk consists of one or more aluminum platters with a magnetizable coating. • 1. Originally, as much as 50 cm in diameter. • Now, 3 – 12 cm. In notebook pc’s or • cameras, they can be as small as 1 -2 cm in • diameter.
Magnetic Disks ---Cont… • 2. Capacity 5 -20 MB only a dozen years • ago. Now, they can be as large as 100 GB. • *** Compare: An ordinary computer science textbook contains about 1 million bytes. 100 GB can store 100, 000 such books, basically, a whole library can be put into one disk. • 3. Fast and reliable. 3600 -100, 000 turns/s • 7, 200 turns/s is typical.
Physical HD • . Track 5 -10 microns Sector A Head 0. 1 – 0. 2 Microns A piece of enlarged track Head movement
Physical HD---cont…. • . Collective movement
Floppy and Tape Drives • They are shrink their roles in PC and soon will be totally disappear. • Currently, 3 ½ “ floppy still a convenient tool for personal use, especially for students. • Tape drive can hold more information. However, the speed has been a major issue.
CD – ROM, DVD-RAM • Because of the capacity, reliability and durability, they have become more and more popular. • Which includes CD-R and CD-RW
The NEW technologies are coming • There a lot of research going on in information storage technologies. • 1. Optical 3 -D storage • 2. Use spin-up and spin-down of atoms. • 3. Magnetic RAM (IBM)
Homework • 1. How many books a 4. 7 GB DVD-ROM can store? (Assuming that each book has an average of 1 million characters) • 2. Compare between HD and CD-RW, can we replace HD with CD-RW? • 3. If you have the choice of the future storage devices and storage media, what kind of properties you like them to have?
