CINAPTUS Technology Consulting Magnetic Storage Concepts How Computers Use Magnets

CINAPTUS Technology Consulting 3/5/20042 Lesson Objectives Introduce magnetism as a memory tool Motivate the need for efficient “permanent” memory Demonstrate the ability to magnetize Demonstrate the use of magnetism to store information Reinforce the idea that computers “speak” binary, requiring us to encode and decode Introduce the topic of electro-magnetism

CINAPTUS Technology Consulting 3/5/20043 Memory Types Short-term memory is used for things that you probably will need to use soon –Humans use their index cards, mnemonics, etc. –Computers use RAM and caches Long-term memory is for things may not need for a long time but don’t want to forget –Humans use notebooks, reference books, libraries, audio tape, video tape, etc. –Computers use floppy disks, hard disks, CDs, etc.

CINAPTUS Technology Consulting 3/5/20044 Disk Anatomy Floppy disks contain a circular piece of plastic embedded with millions of elements of magnetic material Hard disks are similar but consist of hard platters holding the magnetic elements Both types of disks are divided into tracks which are further divided into sectors Both have read/write “heads” on “arms” that are positioned based on addresses

CINAPTUS Technology Consulting 3/5/20045 Why Use Magnets? Magnetic material is readily available and therefore relatively cheap It can also be formed into many shapes We can work with very small magnets Magnets hold state extremely well In summary, magnets: –Don’t take up much space –Don’t cost much –Are reliable –And can be written to and read from quickly

CINAPTUS Technology Consulting 3/5/20046 Making Magnets A ferromagnetic material (such as iron or steel) can be magnetized by exposing it to a magnetic field If its magnetic domains align and “stick”, it becomes a “permanent” magnet It now has north and south poles It also emits a magnetic field which can be “read”

CINAPTUS Technology Consulting 3/5/20047 Exercise Encode your group’s letter using the attached chart Magnetize “bits” by rubbing them with your permanent magnet 20 – 40 times Test each “bit” by trying to pick up a paper clip Read and decode your neighbor’s letter Write their letter on the board

CINAPTUS Technology Consulting 3/5/20048 Exercise Objectives Learn how to magnetize an object and use that property to hold state information Encode to store information in binary and decode to read it back Appreciate the importance of maintaining place order

CINAPTUS Technology Consulting 3/5/20049 Improvement Opportunities RAM vs. disk Optical storage

CINAPTUS Technology Consulting 3/5/ Lesson Summary Computers use magnetism for fairly fast, pretty cheap, long-term storage Magnetic material can be magnetized by exposing it to a strong magnetic field Floppy and Hard Disks consist of millions of tiny elements that can be magnetized Computers store data “permanently” by magnetizing and demagnetizing these elements