storage devices magnetic storage optical storage digital storage
TRANSCRIPT
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 720KB 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, SuperDisks & HiFD disks
--hold up to 750MB (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 DevicesStore 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-ReWritable)
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-ReWritable)
--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