Storage 1
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Transcript of Storage 1
Chapter 7Storage
StorageWhat is storage?
p. 348 Fig. 7-1 Next
Holds data, instructions, and information for future use
Storage medium is physical material used for storage
Also called secondary storage
StorageWhat is capacity?
p. 350 Next
Kilobyte (KB) 1 thousand
Megabyte (MB) 1 million
Gigabyte (GB) 1 billion
Terabyte (TB) 1 trillion
Petabyte (PB) 1 quadrillion
Number of bytes (characters) a storage medium can hold
Exabyte (EB) 1 quintillion
Zettabyte (ZB) 1 sextillion
Yottabyte (YB) 1 septillion
Storage Medium(floppy disks, Zip disks,
hard disks, CDs)
StorageHow does volatility compare?
p. 350 Next
No
nvo
lati
le
Storage medium is nonvolatile—contents retained when power is off
Contents Contents retainedretained
Contents available Contents available to userto user
Memory(most RAM)
(chips on motherboard)
Screen Display
ON OFF
Vo
lati
le Display Display disappearsdisappears
Data andData andinstructions instructions
available to useravailable to user
Display Display appearsappears
Data and instructions Data and instructions erasederased
Memory is volatile—holds data and instructions temporarily
WritingWriting
Process of transferring Process of transferring items from memory items from memory
to storage mediato storage media
WritingWriting
Process of transferring Process of transferring items from memory items from memory
to storage mediato storage media
StorageWhat is a storage device?
p. 350 Next
ReadingReading
Process of transferring Process of transferring items from storage items from storage media to memorymedia to memory
ReadingReading
Process of transferring Process of transferring items from storage items from storage media to memorymedia to memory
Hardware that Hardware that records and records and
retrieves items retrieves items to and from to and from
storage mediastorage media
Functions as source of input
Creates output
Floppy Disk Small files to be transported
Secondary Storage
Primary Storage
Hard Disk
CDs and DVDs
Miniature Storage Media
Tape
Items waiting to be interpretedand executed by the processor
Operating system, applicationsoftware, user data and informationSoftware, backups, movies, music
Digital pictures or small files tobe transported
Backups
Memory (most RAM)
Stores …
StorageWhat is access time?
p. 350
Time it takes storage device to locate item on storage medium
Next
Time required to deliver item from memory to processor
fastertransfer
rates
slowertransfer
rates
Floppy DisksWhat is a floppy disk?
p. 351 Fig. 7-5 Next
Portable, inexpensive storage medium (also called diskette)
Thin, circular, flexible film enclosedin 3.5” wide plastic shell
shutter
shell
liner
magneticcoating
flexible thin film
metal hub
Floppy DisksWhat is a floppy disk drive?
p. 352 Fig. 7-6 Next
Floppy disk drive built intoa desktop computer
External floppy disk drive attaches toa computer with a cable
Also called secondary storage
One floppy drive, named drive A If two floppy drives, second
designated as drive B
Device that reads from andwrites to floppy disk
Floppy Disks
p. 353 Fig. 7-8 Next
What are tracks and sectors?
Trackis narrow
recording bandthat forms fullcircle on disk
Sector stores up to512 bytes
of data
Formatting prepares disk for use and marks bad sectors as unusableClick to view Web Link,click Chapter 7, Click Web Linkfrom left navigation, then click Floppy Disks below Chapter 7
Floppy DisksHow do you compute a disk’s storage capacity?
p. 354 Fig. 7-9 Next
Multiply number of sides, number of tracks, number of sectors per track, and number of bytes per sector For high-density disk: 2 sides 80 tracks 18 sectors per track 512
bytes per sector = 1,474,560 bytes
Characteristics of a3.5-inch High-DensityFloppy Disk
Capacity: 1.44 MB
Sides: 2
Tracks: 80
Sectors per track: 512
Sectors per disk: 2880
Floppy DisksWhat is a write-protect notch?
p. 354 Fig. 7-10 Next
Small opening with a cover that you slide Protects floppy disk from being erased accidentally
hole on thisside meansdisk is high
density
hole on thisside meansdisk is high
density
write-protected
not write-protected
notch closedmeans you
can write onthe disk
notch closedmeans you
can write onthe disk
notch openmeans you
cannot writeon the disk
notch openmeans you
cannot writeon the disk
ExternalZip drive
Zip® DisksWhat is a Zip disk?
p. 355 Fig. 7-11 Next
Magnetic medium that stores 100 MB to 750 MB of data
Zip disks require a Zip drivec—chigh capacity drive that reads from and writes on a Zip disk
Used to back up and to transfer files
Backup is duplicate of file, program, or disk in case original is lost
c
Zip disk
Click to view Web Link,click Chapter 7, Click Web Linkfrom left navigation, then click Zip Disksbelow Chapter 7
Hard DisksWhat is a hard disk?
p. 355 Fig. 7-12 Next
hard disk installedin system unit
High-capacity storage Consists of several inflexible,
circular platters that store items electronically
Components enclosed in airtight, sealed case for protection
Click to view Web Link,click Chapter 7, Click Web Linkfrom left navigation, then click Hard Disk below Chapter 7
Hard DisksWhat are characteristics of a hard disk?
p. 356 Fig. 7-13 Next
Sample Hard Disk Characteristics
Advertised capacity 120 GBPlatters 3Read/write heads 6Cylinders 16,383Bytes per second 512Sectors per track 63Sectors per drive 234,441,648Revolutions per minute 7,200Transfer rate 133 MB per secondAccess time 8.9 ms
actualdisk
capacity
Hard DisksHow does a hard disk work?
p. 357 Fig. 7-14 Next
Step 1.Circuit board controls movement of head actuator and a small motor.
Step 2.Small motor spins platters while computer is running.
Step 3.When software requests a disk access, read/write heads determine current or new location of data.
Step 4.Head actuator positions read/write head arms over correct location on platters to read or write data.
Hard DisksWhat is a cylinder?
p. 357 Fig. 7-15 Next
Vertical section of track through all platters
Single movement of read/write head arms accesses all plattersin cylinder
platter
read/writehead
platter
sides
cylinder
track
sector
Click to view animation