Storage Devices Magnetic Storage Optical Storage Digital Storage

Storage Devices • Magnetic Storage • Optical Storage • Digital Storage

Magnetic Storage Devices Surface is coated with magnetically sensitive material that reacts to a magnetic field. Types: Floppy Disks (Diskettes) Hard Disks External High Capacity Floppy Disks External Hard Disks (Disk Cartridges) Tape Drives

Floppy Disks (Diskettes) --must be formatted divided into tracks and sectors --random access--can access any one spot without scanning through all data --capacity of 720 KB to 1. 44 MB --spin at 300 rpm

Hard Disks --also has tracks and sectors --a stack of rigid disks; sealed --read/write head extremely close, but not touching --newest ones can store up to 256 -320 GB --spin at 15, 000 rpm

External High Capacity Floppy Disks --approximately size of floppy disk --needs drive added --Examples—Zip disks, Super. Disks & Hi. FD disks --hold up to 750 MB (equal to 520 floppy disks)

External Hard Disks (Disk Cartridges) --removable hard disk --some are PC Cards special adaptor to slide card into --example—Jaz disk --up to 500 GB

Tape Drives --work like audiocassette --sequential access --used mainly for back-up --up to 800 GB if compressed --inexpensive alternative

Optical Storage Devices Store data on a reflective surface so it can be read by a beam of laser light. Types: CD-ROM DVD-ROM CD-R (CD-Recordable) CD-RW (CD-Re. Writable) Photo CD DVD-R (DVD-Recordable) DVD-RAM

CD-ROM --compact disk-read-only memory --can be “read” many times, but not changed --same technology as music CDs --Laser senses whether laser is reflecting or scattering light (reflect = 1; scattering = 0) --holds up to 700 MB of data or 80 min. of audio --slower retrieval rate than a hard disk

DVD-ROM --digital video disk read-only memory --can be “read” many times, but not changed --large capacity due to using both sides of the disk & using special data compression technology --two-sided = capacity up to 9. 4 GB (or 17 GB if double-sided & double-layered) --these drives can play CD-ROMs & audio CDs --newest ones may have multiple layers

CD-R (CD-Recordable) --may create your own CDs (data or audio) --once recorded, cannot be changed

CD-RW (CD-Re. Writable) --can write data, then overwrite it with new data --most can be overwritten up to 100 times --may not play on every CD-ROM drive --most cannot store audio data

Photo CD --recordable CD that stores digitized photographs --images viewed from CD-ROM drive --images cannot be erased or changed --can continue to add new images until full --can paste images into other documents

DVD-R (DVD-Recordable) --may create your own DVDs --once recorded, cannot be changed

DVD-RW (DVD-Rewritable) or DVD-RAM --may record, erase and re-record data --DVD-RAM drives can read DVDs, DVD-R disks, CD -R disk, CD-RW disks and standard CDs.

Digital Storage Devices Store data in digital form on a memory chip Types: Memory Sticks USB Portable Flash Drives SD Cards XD Cards Compact Pen Drives

Examples of Digital Storage Devices Up to 16 GB