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