Chapter 7 Objectives Differentiate ( 区分 ) between storage devices and storage media Describe the characteristics ( 特征 ) of magnetic( 磁盘 ) disks Describe the characteristics of a hard( 硬盘 ) disk Discuss various types of miniature ( 缩图 ), external, and removable( 可移动的 ) hard disks Describe the characteristics of optical( 光碟片 ) discs Differentiate among CD-ROMs, recordable( 可记录的 ) CDs, rewritable CDs, DVD-ROMs, BD-ROMs, HD DVD-ROMs, recordable DVDs, and rewritable DVDs Identify the uses of tape( 磁带 ) Discuss PC Cards, ExpressCard modules, and the various types of miniature storage media Identify uses of microfilm ( 缩影胶卷 ) and microfiche ( 单片缩影胶片 ) Next

Storage What is storage? p Fig. 7-1 Next  Holds data, instructions, and information for future use 保存数据、指令和信息，以备将来使用。  Storage medium ( 存储介质 ) is physical material used for storage 存储介质 （ Storage medium ）可用于存储的物理材料。  Also called secondary ( 辅存 ) storage 也称为辅助存储（ secondary storage ）。

Storage What is capacity ( 容量 ) ? p. 356 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 K = 1024 = 2 10 M = 1024 x 1024 = 2 20 G = 1024 x 1024 x 1024 = 2 30 T = 1024 x 1024 x 1024 x 1024 = 2 40 P = 1024 x 1024 x 1024 x 1024 x 1024 = 2 50 E = 1024 x 1024 x 1024 x 1024 x 1024 x 1024 = 2 60

Storage Medium (floppy disks, Zip disks, hard disks, CDs) Storage How does volatility ( 挥发性 ) compare? p. 356 Next Nonvolatile  Storage medium is nonvolatile ( 非易失性 ) —contents ( 内容 ) retained ( 保持 ) when power is off Contents retained Contents available to user Memory (most RAM) (chips on motherboard) Screen Display ONOFF Volatile Display disappears Data and instructions available to user Display appears Data and instructions erased  Memory is volatile—holds data and instructions temporarily ( 临时 )

Writing Process of transferring items from memory to storage media Writing Storage What is a storage device? p. 356 Next Reading Process of transferring items from storage media to memory Reading Hardware that records and retrieves ( 检索 ) items to and from storage media Functions as source of input Creates output

Floppy Disk ( 软盘 ) Small files to be transported Secondary Storage Primary Storage Hard Disk Flash Memory Cards and USB Flash Drives CDs and DVDs Tape ( 磁带 ) Items waiting to be interpreted and executed by the processor Operating system, application software, user data and information Digital pictures or files to be transported Software, backups, movies, music Backups ( 备份 ) Memory (most RAM) Stores …Transfer rates Storage What is access ( 访问时间 ) time? p. 357 Fig. 7-4  Time it takes storage device to locate ( 定位 ) item on storage medium ( 媒介 ) Next  Time required to deliver ( 递送 ) item from memory to processor faster transfer rates slower transfer rates

Magnetic( 磁盘 ) Disks p. 357 Fig. 7-5 Next What are tracks ( 轨道、磁道 ) and sectors ( 扇区 ) ? Formatting ( 格式化 ) prepares disk for use Track is narrow recording band that forms full circle on disk 是窄的记录 带，在磁盘 上形成完整 的圆环 Sector stores up to 512 bytes of data 可存储多 达 512 字 节的数据

Magnetic Disks What is a cylinder ( 柱面 ) ? p. 360 Fig. 7-9 Next  Vertical ( 垂直剖面 ) section of track through all platters  Single movement of read/write head arms accesses all platters in cylinder platter ( 圆形磁盘片 ) read/write head( 磁头 ) platter sides Cylinder( 柱面 ) Track( 磁道 ) Sector( 扇区 )

Perpendicular ( 垂直 ) recording Magnetic Disks What is a hard disk? ( 硬盘 ) Next hard disk mounted ( 安装在 ) in system unit  High-capacity ( 大容量 ) storage 高性能的存储器  Consists of several inflexible ( 刚硬的 ), circular platters ( 圆形磁盘片 ) that store items electronically 包含一些固定的圆盘，圆盘上可存储电子信息  Components enclosed in airtight ( 密封的 ), sealed ( 密封盒 ) case for protection 组件有密闭的外壳保护 Longitudinal ( 纵向、水平 ) recording

Magnetic Disks What are characteristics ( 特征 ) of a hard disk? p. 359 Fig. 7-7 Next Sample Hard Disk Characteristics Advertised ( 标榜 ) capacity500 GB Platters ( 圆形磁盘片 ) 4 Read/write heads8 Cylinders ( 柱面 ) 16,383 Bytes per second512 Sectors per track63 Sectors per drive973,773,168 Revolutions ( 转速 ) per minute7,200 Transfer rate300 MB per second Access time8.5 ms actual disk capacity

Magnetic Disks How does a hard disk work? 硬盘如何工作 Next Step 1. Circuit board controls movement of head actuator and a small motor. 电路板控制着磁头和小马 达的运动 Step 2. Small motor spins ( 旋转 ) platters while computer is running. 当运行计算机时， 小马达转动盘片 Step 3. When software requests a disk access, read/write heads determine current or new location of data. 软件请求磁盘数据时， 读写头将寻找数据位置 Step 4. Head actuator positions read/write head arms over correct location on platters to read or write data. 系统从磁头位置读取或写 入数据

Magnetic Disks What is a cylinder ( 柱面 ) ? p. 360 Fig. 7-9 Next  Vertical ( 垂直剖面 ) section of track through all platters 通过所有盘片（ platter ）的垂直剖面  Single movement of read/write head arms accesses all platters in cylinder 一个磁头（读写头）的运动可访 问一个磁柱中的所有盘片 platter ( 圆形磁盘片 ) read/write head( 磁头 ) platter sides Cylinder( 柱面 ) Track( 磁道 ) Sector( 扇区 )

Magnetic Disks What is a head crash( 碰撞 )? p Fig Next  Spinning ( 旋转 ) creates cushion ( 气垫空气 ) of air that floats read/write head above platter  Occurs when read/write head touches platter surface  A smoke particle ( 微粒 ), dust particle, or human hair could render drive unusable  Clearance between head and platter is approximately ( 大约 ) two-millionths of an inch

Next Magnetic Disks What is a miniature( 微型 ) hard disk? p. 362 Fig  Provide greater storage capacities than flash memory  Smaller than notebook computer hard disks  A pocket hard drive is a self-contained ( 独立的 ) unit Click to view Web Link, click Chapter 7, Click Web Link from left navigation, then click Pocket Hard Drives below Chapter 7

Magnetic Disks What are external hard disks( 外置硬盘 ) and removable ( 抽取式 ) hard disks? p. 363 Fig Next External hard disk—freestanding ( 独立式、不需要依靠支持物 ) hard disk that connects to system unit External hard disk— 独立的硬盘，可连接到系统单元。 Removable hard disk—hard disk that you insert ( 插入 ) and remove from hard disk drive Removable hard disk— 可从硬盘驱动器中 拔插。  Used to back up ( 备份 ) or transfer files

Magnetic Disks What is online storage? ( 在线存储 ) p Fig Next  Others can be authorized ( 经授权 的 ) to access your data 其他被授权的人也可访问你的数据  Service on Web that provides storage for minimal monthly fee 基于 Web 服务的小月租费的存储  Files can be accessed from any computer with Web access 可以从任何可上网的计算机中访问存储文件  Large files can be downloaded instantaneously ( 即时 ) 可瞬间下载大文件

Magnetic Disks What is a floppy disk? ( 软盘 ) p. 365 Fig Next  Portable ( 便携 ), inexpensive ( 便宜 ) storage medium (also called diskette 磁碟 ) 便携式，廉价的存储介质 Thin ( 薄 ), circular ( 圆形的 ), flexible film ( 柔韧性薄膜 ) enclosed in 3.5” wide plastic ( 塑胶 ) shell 薄，圆形，柔软的薄膜，由 3.5 英寸的全塑外 壳封闭

Push the same button to close the tray. Optical ( 光碟片 ) Discs 光盘 What are optical discs? p. 366 Fig Next  Most PCs include an optical disc drive 大部分 PC 机都包含光盘驱动器  Flat, round, portable metal discs made of metal, plastic ( 塑胶 ), and lacquer ( 油漆、光洁 ) 用金属、塑料、漆作成的扁的、圆的、便携 式的盘  Can be read only or read/write 可以是只读形式或读 / 写形式 Insert the disc, label side up. Push the button to slide ( 滑出 ) out the tray ( 托盘 ).

Optical Discs How does a laser ( 激光 ) read data on an optical disc? 如何通过激光读取光盘中的数据 ? laser diode ( 激光二极管 ) laser diode prism 棱镜 prism light- sensing diode 01 lens ( 透镜、镜头 ) lens pit 凹坑 land disc label Step 1. Laser diode ( 激光二 极管 ) shines ( 发光 ) a light beam ( 线偏振光 束 ) toward disc. 激光二极管发出光束 照亮光盘 Step 2. If light strikes a pit, it scatters ( 发散 ). If light strikes a land, it is reflected ( 反射 ) back toward diode. 如果照到一个小 坑，则光线分散 ，如果照到一个 小包，则光线被 反射回 Step 3. 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. 有反射光线的地方被 认为是 1 ，无反射光 线的地方被认为是 0

Optical Discs How is data stored on an optical disc? 数据是如何存储在光盘中的 p. 367 Fig Next  Typically ( 代表性地 ) stored in single track 通常存在单一轨道。  Track divided into evenly ( 均匀 地 ) sized sectors that store items 轨道被分成大小均匀的扇区，以存 储不同的项目。 single track spirals ( 螺旋 ) to edge ( 边缘 ) of disc disc sectors

Optical Discs What is a CD-ROM? p. 369 Fig Next  Compact ( 紧凑 ) disc read-only memory  Cannot erase or modify contents ( 内容 )  Typically holds 650 MB to 1 GB  Commonly ( 一般 ) used to distribute ( 分发 ) multimedia and complex software

Optical Discs What is the data transfer rate of a CD-ROM drive? 48X 表示 CD 读取 / 写入速度，读作 “48 倍速 ” ，表示是软盘的 48 倍读写速度。 1 倍速 1X=150KB/s （这是 3.5 英寸软盘的读写速度）。 48X=7200KB/s 。 p. 369 Next 75X Ranges ( 范围 ) from 48X to 75X or faster 75  150 KBps = 11,250 KBps or MBps 75X is 150 KBps (KB per second) 48X: 48  150 KBps = 7,200 KBps or 7.2 MBps

Optical Discs What is a DVD-ROM (digital versatile ( 通用的、万能的 ) disc-ROM or digital video disc-ROM)? p. 372 Fig Next  Must have DVD-ROM drive or DVD player to read DVD-ROM  Stores databases, music, complex software, and movies  Blu-ray discs ( 蓝光光碟是 DVD 之后的下一代光盘 格式之一 ) have storage capacity of up to 100 GB  HD-DVD discs have storage capacity of up to 60 GB  UMD ( 通用 媒体光碟 ) can store up to 1.8 GB

Tape What is tape( 磁带 )? p. 374 Fig Next  Magnetically ( 磁 ) coated ( 涂上一层 ) plastic ( 塑胶 ) ribbon ( 带子 ) capable of storing large amounts ( 数量 ) of data at low cost ( 低成本 )  Primarily used for backup ( 备份 )

Tape How is data stored on a tape? p. 374 Next  Sequential access ( 顺序存取 )  Unlike direct access — used on hard disks, CDs, and DVDs — which can locate ( 定位 ) particular ( 精确的 ) item immediately  Reads and writes data consecutively ( 连续 ), like music tape

Miniature Mobile Storage Media What are common types of flash memory cards? p. 376 Fig Next CompactFlashSecure DigitalxD Picture Card Memory StickMemory Stick PRO Duo

Miniature Mobile Storage Media What is a USB Flash Drive? p. 377 Fig Next  Plugs in a USB port on a computer or mobile device  Storage capacities up to 64 GB  May ( 也许 ) eventually ( 最终 ) make the floppy disk obsolete ( 被淘汰 )

Miniature Mobile Storage Media What is a smart card( 智能卡 )? p. 378 Fig Next  Stores data on microprocessor ( 微处理器 ) embedded in small card  Input, process, output, and storage capabilities

Summary of Storage Internal hard disks External and removable hard disks Floppy disks CD-ROMs Recordable and Rewritable CDs DVD-ROMs Blu-ray Discs (BDs) HD DVD discs Recordable and Rewritable DVDs Tape PC Cards and ExpressCard modules Flash memory cards and USB flash drives Chapter 7 Complete Smart cards, microfilm, and microfiche