Introduction To Data Storage Cpu And

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Introduction to Computing INTRODUCTION TO Data Storage CPU AND MICROPROCESSOR Memory • Used to store data, instructions, and information – The operating system and other system software – Application programs – Data being processed by application programs • Bytes are stored at specific locations or addresses Memory Memory • Size of memory is measured by the number of bytes available Memory Memory • Volatile memory – contents are lost when the computer is powered down • Nonvolatile memory – contents are not lost when the computer is powered down Memory Random Access Memory (RAM) • The memory chips in the system unit • When the computer starts, operating system files are loaded from a hard disk into RAM Memory Random Access Memory (RAM) • RAM Chips – Smaller in size than processor chips – Packaged on circuit boards called single inline memory modules (SIMMs) or dual inline memory modules (DIMMs) Memory Random Access Memory (RAM) • Configuring RAM – The more RAM, the more programs and files a computer can work on at once – Software usually tells you how much RAM is required – Necessary RAM depends on what type of work the computer is used for Affecting Processing Speed Virtual RAM • Computer is out of actual RAM • File that emulates RAM • Computer swaps data to virtual RAM – Least recently used data is moved 5A-30 Memory Nonvolatile memory • • • • Holds data when power is off Read Only Memory (ROM) Basic Input Output System (BIOS) Power On Self Test (POST) 5A-31 Memory Read-Only Memory (ROM) • Cannot be modified • Contents not lost when the computer is turned off • PROM • EPROM • EEPROM Bus Address Bus Data Bus Bay Cache Memory Helps speed computer processes by storing frequently used instructions and data  Also called memory cache How Computers Process Data Flash memory • Data is stored using physical switches • Special form of nonvolatile memory • Camera cards, USB key chains 5A-35 Affecting Processing Speed The bus • • • • • Electronic pathway between components Expansion bus connects to peripherals System bus connects CPU and RAM Bus width is measured in bits Speed is tied to the clock 5A-36 Teachers Discovering Computers Integrating Technology in the Classroom 3rd Edition Secondary Storage WHAT IS STORAGE?  The media on which data, instructions, and information are kept  The devices that record and retrieve data, instructions, and information  Like a filing cabinet WHAT IS STORAGE? Storage Media and Devices • Storage medium – Also called secondary storage – Physical material • Storage device – Mechanism used to record and retrieve – Capacity measured in megabytes or gigabytes Storage Devices Floppy Disk Hard Disk CD / DVD Miniature Cards Smart Cards Floppy Disks What is a floppy disk drive?  Device that reads from and writes to floppy disk    One floppy drive, named drive A If two floppy drives, second designated as drive B Floppy disk drive built into a desktop computer Also called secondary storage External floppy disk drive attaches to a computer with a cable p. 7.06 Fig. 7-6 Next WHAT IS STORAGE? Floppy Disks • Portable, inexpensive storage medium consisting of a thin, circular, flexible film enclosed in a squareshaped plastic shell • Several sizes – 8-inch – 5.25-inch – 3.5-inch shutter shell liner magnetic coating metal hub flexible thin film p. 7.05 Fig. 7-5 Floppy Disks How does a floppy disk drive work? Step 1. When you insert the floppy disk into drive, shutter moves to the side to expose the recording surface on disk. Step 6. Read/write heads read data from and write data on floppy disk. Step 2. When you initiate a disk access, circuit board on drive that contains electronics sends signals to control movement of read/write heads until they barely touch surface (film) inside floppy disk’s shell. Step 5. Motor positions read/write heads over correct location on recording surface of disk. Step 3. For write Step 4. Motor spins a instructions, circuit board verifies whether or not disk can be written on. shaft, which causes surface inside floppy disk’s shell to spin. p. 7.06 Fig. 7-7 Next Floppy Disks What are tracks and sectors? Track is narrow recording band that forms full circle on disk Click to view Web Link, then click Floppy Disks below Chapter 7 p. 7.07 Fig. 7-8 Sector stores up to 512 bytes of data Formatting prepares disk for use and marks bad sectors as unusable Next Floppy Disks How do you compute a disk’s storage capacity?  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 a 3.5-inch High-Density Floppy Disk Capacity: 1.44 MB Sides: 2 Tracks: 80 Sectors per track: 18 Sectors per disk: 2880 p. 7.08 Next WHAT IS STORAGE? Characteristics of a Floppy Disk • Uses magnetic patterns to store data • Formatting – Track – Sector • Write-protection • Guidelines for floppy disk care • Floppy disk drive Floppy Disks  What is a write-protect notch? Small opening with a cover that you slide Protects floppy disk from being erased accidentally   write-protected notch open means you cannot write on the disk not write-protected hole on this side means disk is high density notch closed means you can write on the disk p. 7.08 Fig. 7-10 Next Zip® Disks ® What is a Zip disk?   Magnetic medium that stores 100 MB or 250 MB of data or 750 MB Used to back up and to transfer files  Zip disk Backup is duplicate of file, program, or disk in case original is lost c   Zip disks require a Zip drive — high capacity drive that reads from and writes on a Zip disk REV disks (35GB) are similar. p. 7.09 Fig. 7-11 c c External Zip drive Next WHAT IS STORAGE? High-Capacity Removable Disks • Capacities greater than 100 MB • Many uses – Graphics, audio, or video – Transporting files – Backups • Zip drive WHAT IS STORAGE? Hard Disks • Provide large storage capacity and high speed data access • Sizes range from 30 GB to 100 GB • Consists of several inflexible, circular disks, called platters • Magnetic storage device • Formatting Hard Disks How does a hard disk work? Step 3. When software requests a disk access, read/write heads determine current or new location of data. Step 2. Small motor spins platters while computer is running. Step 4. Head actuator positions read/write head arms over correct location on platters to read or write data. Step 1. Circuit board controls movement of head actuator and a small motor. p. 7.11 Fig. 7-14 Next Hard Disks  What is a cylinder?  Vertical section of track through all platters  Single movement of read/write head arms accesses all platters in cylinder platter track sector read/write head platter sides p. 7.11 Fig. 7-15 cylinder Next Hard Disk Partitions and Logical Drives  When installing an operating system on a new computer or after recovering from a hard disk failure, prepare the hard disk for use by: • • • • Partitioning the hard disk Creating logical drives Formatting logical drives A maximum of 4 primary partitions can be placed on a hard disk, but only 1 extended partition – The way the Master Boot Record is structured determines this limitation. Disk Partitioning Partition disks to divide total storage space Primary partition — the system’s boot drive, used for system startup Extended partition — the remaining drive space after you create the primary partition Logical Disk Drives A disk partition must be assigned a logical drive identifier A primary partition is treated as a single logical drive An extended partition can be divided into multiple logical drives (drives D and E in figure) Logical Drive Format Low-level format: • Prepares the hard disk before disk partitions can be defined • Primarily the responsibility of the hard disk manufacturer High-level format: • Logical drive formatting that prepares the drive for use by the operating system • Creates the file system root directory and the files used to track disk space use Hard Disks What are characteristics of a hard disk? Sample Hard Disk Characteristics Advertised capacity Platters Read/write heads Cylinders Bytes per sector Sectors per track Sectors per drive Revolutions per minute Transfer rate second Access time 40 GB 2 4 16,383 512 63 78,165,360 7,200 100 MB per actual disk capacity 9 ms Next p. 7.10 Fig. 7-13 Head Crash on a Hard Disk  What is a head crash?   Occurs when read/write head touches platter surface Spinning creates cushion of air that floats read/write head above platter   Clearance between head and platter is approximately two-millionths of an inch A smoke particle, dust particle, or human hair could render drive unusable hair read/write head dust clearance smoke platter p. 7.12 Fig. 7-16 Next Hard Disk Cache What is a disk cache?  processor Portion of memory that processor uses to store frequently accessed items disk cache first request for data—to disk cache in RAM second request for data—to HARD disk hard disk p. 7.12 Fig. 7-17 Next Magnetic Disk Controllers What is a disk controller? Chip and circuits that control transfer of items from disk EIDE (Enhanced Enhanced Integrated Drive Electronics) controller supports four hard disks, provides connections for CD and DVD drives p. 364 SATA (Serial Serial Advanced Technology Attachment) controller uses serial signals to transfer data, instructions, and information SCSI (Small Computer System Interface) controller supports up to fifteen devices including hard disks, CD and DVD drives, tape drives, printers, scanners, network cards Next External Hard Disks What is an external hard disk ?    Used to back up or transfer files Connects to USB 2.0 or Firewire port Maxtor One-Touch Backup: 250GB, Cost: < $200.00 www.Seagate.com External hard disk—freestanding hard disk that connects to system unit with a USB 2.0 cable p. 7.13 Fig. 7-18 Next Removable Magnetic Disks  What are external hard disks and removable hard disks?  Used to back up or transfer files Removable hard disk—hard disk that you insert and remove from hard disk drive External hard disk—freestanding hard disk that connects to system unit Click to view Web Link, click Chapter 7, Click Web Link from left navigation, then click Hard Disks below Chapter 7 p. 364 Fig. 7-17 Next WHAT IS STORAGE? CDs and DVDs • • • • • Optical storage media Used to distribute software Laser reads pits on the surface Used on multimedia computers Several types – CD-ROM – DVD-ROM CDs and DVDs How does a laser read data on a CD or DVD? disc label lens pit 0 prism lightsensing diode Step 1. Laser diode shines a light beam toward disc. p. 7.16 Fig. 7-21 laser diode lens land Step 3. Step 2. If light strikes a pit, it scatters. If light strikes a land, it is reflected back toward diode. 1 prism lightsensing diode laser diode Reflected light is deflected to a light-sensing diode, which sends digital signals of 1 to computer. Absence of reflected light is read as digital signal of 0. Next CDs and DVDs How is data stored on a CD or  Typically stored in DVD? single track  Track divided into evenly sized sectors that store items Single track spirals to edge of disc The track on a DVD is 7.5 miles long ! p. 7.16 Fig. 7-22 disc sectors Next WHAT IS STORAGE? Care of CDs and DVDs • Can last from 5 to 100 years if properly cared for • Never bend a disc • Avoid extreme temperatures and humidity • Keep away from contaminants • Do not stack or touch discs • Use a protective case WHAT IS STORAGE? CD-ROM • Compact disc readonly memory • Can contain text, graphics, video, as well as sound • Can hold 650 MB of data • Used for today’s complex software WHAT IS STORAGE? CD-R and CD-RW • Compact disc-recordable – Can write on each part of the disc only one time – Cannot be erased • Compact disc-rewriteable – Can write on multiple times – Erasable disc WHAT IS STORAGE? DVD-ROM and DVD+RW • Digital video disc read-only memory (DVDROM) – Can store from 4.7 GB to 17 GB – High quality – DVD-ROM drives – May replace CDs, VCRs, and VHS tapes • Digital video disc+rewritable (DVD+RW) – Can write on multiple times – Erasable disc WHAT IS STORAGE? Miniature Mobile Storage Media WHAT IS STORAGE External and Removable Hard Disks • External Hard Disk – Separate hard disk that connects to a USB or FireWire port by cable – USB Drives File System Types Primary partitions and logical drives must be formatted so the operating system can use them Formatting creates the file system by adding information about how files should be stored on the drive to organize and manage disk storage File system types include: • FAT 16, FAT32 and NTFS (Windows XP) • Ext3 and ReiserFS (Linux) created by Hans Reiser – Note: Hans Reiser was on trial in Feb 2008 for murdering his wife, Nina Reiser (from Russia). Reiser is/was a computer programming genius entering Univ California at Berkeley at age 14 File and Directory Permissions NTFS allows you to set permission bits on system resources In NTFS, you can protect files so that only certain users or groups of users can read them Concerns: • If permissions are applied improperly, users may take security for granted • Improperly set permissions can disrupt an operating system Disk Convert Utility Information about the files on an NTFS volume and their attributes is stored in the MFT Convert utility — used to convert a partition or logical drive from FAT or FAT32 to NTFS  convert drive /FS:NTFS [/v]  convert C: /FS:NTFS Disk Convert Utility Yes ! It works ! Information about the files on an NTFS volume and their attributes is stored in the MFT Convert utility — used to convert a partition or logical drive from FAT or FAT32 to NTFS  convert drive /FS:NTFS [/v]  convert C: /FS:NTFS Yes ! It works ! Disk Defragmenter Utility As files are created and deleted, a partition can become severely fragmented Fragmented files are no longer located in contiguous clusters You can use the Disk Defragmenter utility to defragment hard disks and put files back together in a contiguous format Disk Defragmenter What is a Disk Defragmenter ?  Reorganizes files and unused space into contiguous sectors on hard disk so programs run faster. file before defragmenting fragmented disk file after defragmenting p. 8.17 Fig. 8-19 Next Chkdsk Utility You can use the Chkdsk utility in Windows NT/2000/XP to: • Create and display a status report for a disk based on its file system • List and correct errors on the disk • Display the status of the disk in the current drive • Click Start, click Run, type: chkdsk /F, Click OK Disk Cleanup Use the Disk Cleanup utility to recover the disk space used by: • • • • Temporary files Unused applications Files in the Recycle Bin Files you downloaded as part of Web pages • Files created when Chkdsk attempted to recover lost file fragments (e.g. FILE0001.CHK) CDs and DVDs What are CDs and DVDs?    Flat, round, portable metal discs with protective plastic coating Can be read only or read/write Push the button to slide out the tray. Insert the disc, label side up. Most PCs include CD or DVD drive, most play audio CDs Push the same button to close the tray. p. 7.15 Fig. 7-20 Next Magnetic Tape How is data stored on a tape?  Sequential access  Reads and writes data consecutively, like music tape  Unlike direct access — used on floppy disks, Zip disks, hard disks, CDs, and DVDs — which can locate particular item immediately Popular Types of Tape Name Digital audio tape Digital linear tape Linear tape-open Quarter-inch cartridge Travan p. 7. 24 Fig. 7-30 Abbreviation DAT DLT LTO QIC TR Storage Capacity 2 GB to 240 GB 20 GB to 220 GB 100 GB to 200 GB 40 MB to 25 GB 8 GB to 40 GB Next PC Cards What is a PC Card? (thickness is main difference)   Adds capabilities to computer Credit-card-sized device commonly used in notebook computers PC Cards Category Thickness Type I 3.3 mm Type II 5.0 mm Type III 10.5 mm p. 7.24 Figs. 7-31–7-32 Use RAM, SRAM, flash memory Modem, LAN, SCSI, sound, TV turner, hard disk, or other storage Rotating storage such as a hard disk Next Home-Task: Go through Chapter 7 of “Discovering Computers”