1. Magnets used to store data ? Magnet with unknown state Current N S S N 0 1

2. Binary Representation of Data one bit1 or 0 only 2 choices two bits00, 01, 10, 11 4 choices three bits 000, 001, 010, 011, 100, 101, 110, 111 8 choices n bits has 2 n choices For example, 5 bits has 2 5 = 32 choices... more than enough to represent all the letters of the alphabet

3. Binary representation of lower case letters 5-bit Science Saturday code: ex: k = 01011 0 1 011

4. Magnetic Data Storage A computer hard drive stores your data magnetically Disk NS direction of disk motion Write Head 0010100110__ Bits of information NS Read Head Signal

5. Scaling Down to the Nanoscale Increases the amount of data stored on a fixed amount of real estate ! Now ~ 50 billion bits/in 2, future target more than 1 trillion bits/in 2 25 DVDs on a disk the size of a quarter, or all Library of Congress books on a 1 sq ft tile!

6. NEW! Multi State Representation of Data Disk Write Head Read Head == 0 1 direction of disk motion 1032 0 1 2 3 "CLUSTERS"

7. Multi state representation of lower case letters ……………