当前位置:首页 >> 其它课程 >>

《信息技术与应用导论》(第7版 影印版)-ch4 storage hardware-preserving data and information


STORAGE HARDWARE Preserving Data and Information

Chapter 4

review
CRT 点距 驱动程序 像素 打印机 刷新频率 分辨率 终端

Main contents
4.1 storage fundamentals 4.2 tape s

torage (×) 4.3 diskette storage 4.4 hard disks 4.5 optical disks 4.6 the importance of backup 4.7 other forms of secondary storage

Terms—p4.28-p4.29
access time 访问时间 ASCII files ASCII码文件(纯文本文件) audio files 声音文件 cartridge tape units 卡带单元 data files 数据文件 direct access storage 直接访问存储

Terms—p4.29
disk drive 磁盘驱动器 diskette 软盘,磁盘 EIDE- enhanced integrated drive electronics 增强型IDE接口 executable files 可执行文件 FAT-file allocation table 文件分配表 formatting 格式化

Terms—p4.30
hard disk 硬盘 hard disk cartridge 硬盘盒 high-density diskette 高密盘 image files 图像文件 latency 潜伏期 magnetic tape 磁带

Terms—p4.30-p4.31
program files 程序文件 RAID-redundant array of inexpensive disks 廉价磁盘冗余阵列 read 读 SCSI-small computer system interface 小型计算机系统接口 secondary storage 辅助存储 sectors 扇区

Terms—p4.31
seek time 寻道时间 sequential storage 顺序存储 source program files 源程序文件 tracks 磁道 video files 视频文件 virtual memory 虚拟内存 write 写

4.1

Storage Fundamentals

Key Question: What is the

difference between primary and secondary storage, and what are the basic types of files ?

the difference between primary and secondary storage

The data you are working on is stored in RAM in an electrical state during processing . Because RAM is an electrical state , data in RAM disappears when you turn off the power to your computer . (P4.2 )

the difference between primary and secondary storage Therefore ,before you turn your microcomputer off , you must save your work onto a storage device that stores data permanently—such as a diskette or a hard disk—rather than electrically . When saved to a secondary storage device , your data will remain intact(完整无缺的) even when the computer is turned off. (P 4.2)

Data access method
Sequential storage (P4.3) – the data is stored in sequence, such as alphabetically. – tape storage falls in this category.

Data access method
Direct access storage (P4.3) – Also called random access storage, the computer can go directly to the information you want. – Hard disks and other types of disks, generally fall in this category.

Types of Files (P4.6) A file is a collection of data or information treated as a unit by the computer .

Types of Files (P4.6) Program files
– Program files contain software instructions . – Source program files(源程序) contain high level computer instructions in their original form , as written by the programmers . These instructions must be translated into machine language instructions in order for the processor to use them . – The files that contain the machine language instructions are called executable files.

Types of Files (P4.6) Data files
– Data files ,often called document files , contain data ,not programs— that is , they contain material that you or someone else has created and stored using applications software.

Types of Files (P4.6) ASCII files
– ASCII files are text—only .The characters are in ASCII code .This file format is used to transfer documents between in compatible platforms ,such as IBM and Macintosh.

Types of Files (P4.6) Image files
– Image files contain digitized graphics.

Audio and video files
– Audio file contain digitized sound .Video files contain digitized video images .

File name
A file name consists of a unique name, which describes its contents ,and a three-character extension, which describes its type.

Examples of pc file extensions
.aiff 声音文件 .ani 动画鼠标 .arj 压缩文件 .avi 电影文件 .bak 备份文件 .bmp 图象文件 画图/看图软件

Examples of pc file extensions
.cab 压缩文件 Winzip .com DOS命令文件 自执行 .dbf 数据库文件 .doc 文档文件 Word .exe 执行文件 自执行 .fon 字体文件

Examples of pc file extensions
.gif 256色图象文件 .htm 网页 .html 网页 .ico 图标 .jpeg 压缩过的图象文件 .jpg 压缩过的图象文件

Examples of pc file extensions
.mid 声音文件 .mov Quicktime影像文件 .mp3 压缩音乐文件 .mpeg 影像 .mpg 影像 .pdf 便携式文档格式 .ppt Power Point 文件

Examples of pc file extensions
.psd Photoshop文件 .ra Real Audio声音文件 .ram Real Audio影像文件 .rar 压缩文件 Winrar .swf Flash动画文件 .sys 系统文件

Examples of pc file extensions
.tif 高质量图象文件 .tiff 高质量图象文件 .tmp 暂存文件 .txt 纯文本文件 .wav 未压缩的声音文件 .xls Excel 文件 .zip 压缩文件 Winzip

What you can do with files?(p4.7)
In addition to naming, saving ,and opening files, file management also involves copying, renaming, and deleting files, and printing files.

What you can do with files?(p4.7)
If your files are huge , taking up a lot of space on your hard disk, you may want to use special software to compress them.

What you can do with files?(p4.7)
Additional file-management procedures involve importing a file so that you can use it in the current software application and exporting a file to a software format different from the current one.

4.3 diskette storage
What are tracks and sectors formatting

Tracks(P4.10)
On a disk, data is recorded in rings called tracks, which are neither visible grooves (凹槽) nor a single spiral(螺 旋线). Rather, they are closed concentric(同心的) rings.

Tracks(P4.10)
The numbers of tracks on a diskette is measured in TPI, or tracks per inch. The higher the TPI, the more data the diskette can hold. example: 3 ? inch diskette has 80 tracks one side

Sectors (p 4.10)
Each track is divided into sectors. Sectors are invisible wedge-shaped sections used by the computer for storage reference purposes. example: 3 ? diskette has 18 sectors one track, each sector holds 512 bytes of data.

Tracks and sectors (p4.10)
When you save data from your computer to a diskette, it is distributed by tracks and sectors on the disk.

Formatting (4.11)
Formatting, or initializing, means preparing the disk so that the computer’s operating system software can write information on it. This includes defining the tracks and sectors on it, as well as setting up the FAT (File Allocation Table文件分 配表).

4.4 hard disks-p4.12

Hard disks (p4.12-p4.13)
Hard disks are thin but rigid metal or glass platters covered with a substance that allows data to be held in the form of magnetized spots.

Hard disks (p4.12-p4.13)
Hard disks are also tightly sealed(密封) within an enclosed unit to prevent any foreign matter-dust or smoke, for example-from getting inside. Data maybe recorded on both sides of the disk platters.

Cylinder method (p4.14)
Secondary storage systems that use several hard disks don’t use the sector method to locate data. Rather they use what is known as the cylinder(柱面) method.

Cylinder method (p4.14)
Because the access arms holding the read/write heads all move together, the read/write heads are always over the same track on each disk at the same time.

Cylinder method (p4.14)
All the tracks with the same track number, lined up one above the other, thus form a cylinder.

review
磁盘驱动器 硬盘 扇区 磁道

Terms-p4.28-p4.31
CD-R—compact disk recordable 可记录式光盘 CD-ROM 只读光盘 CD-RW-可写光盘 DVD-ROM 只读数字视盘 flash memory card 闪存卡 optical disk 光盘

Microcomputer hard disk variations: power & portability
If you have a microcomputer with limited hard disk capacity, the following options provide additional power or portability: external hard disk drives Removable disks (p4.16)

external hard disk drives (p4.16)
If you don’t have room in the system unit for another internal hard disk but need additional storage, consider adding an external hard disk drive. You can also attach several external hard drives via a SCSI interface.

Removable disks (p4.16)
Hard disk cartridges, or removable hard disks, consist of one or more platters enclosed along with read/write heads in a hard plastic case. The case is inserted into an internal cartridge drive connected to a microcomputer.

Virtual memory: using disk space to increase RAM(p4.17)
Virtual memory uses disk space to extend primary memory (RAM), enabling users to run larger software programs than would otherwise be possible.

About virtual memory

Virtual memory
Virtual memory is a common part of most operating systems on desktop computers. It has become so common because it provides a big benefit for users at a very low cost.

Virtual memory
In this article, you will learn exactly what virtual memory is, what your computer uses it for and how to configure it on your own machine to achieve optimal performance.

Virtual memory
Most computers today have something like 32 or 64 megabytes of RAM available for the CPU to use. Unfortunately, that amount of RAM is not enough to run all of the programs that most users expect to run at once.

Virtual memory
For example, if you load the operating system, an e-mail program, a Web browser and word processor into RAM simultaneously, 32 megabytes is not enough to hold it all.

Virtual memory
If there were no such thing as virtual memory, then once you filled up the available RAM your computer would have to say, "Sorry, you can not load any more applications. Please close another application to load a new one."

Virtual memory
With virtual memory, what the computer can do is look at RAM for areas that have not been used recently and copy them onto the hard disk. This frees up space in RAM to load the new application.

Virtual memory
Because this copying happens automatically, you don't even know it is happening, and it makes your computer feel like it has unlimited RAM space even though it only has 32 megabytes installed. Because hard disk space is so much cheaper than RAM chips, it also has a nice economic benefit. -

Virtual memory
The read/write speed of a hard drive is much slower than RAM, and the technology of a hard drive is not geared toward accessing small pieces of data at a time. If your system has to rely too heavily on virtual memory, you will notice a significant performance drop.

Virtual memory
The key is to have enough RAM to handle everything you tend to work on simultaneously - Then, the only time you "feel" the slowness of virtual memory is when there's a slight pause when you're changing tasks. When that's the case, virtual memory is perfect.

Virtual memory
When it is not the case, the operating system has to constantly swap information back and forth between RAM and the hard disk. This is called thrashing(颠簸), and it can make your computer feel incredibly slow.

4.5 optical disks(p4.18)
an optical disk is a removable disk on which data is written and read through the use of laser beams.

optical disks
In the principal types of optical disk technology, a highpower laser beam is used to represent data by burning tiny pits(坑) into the surface of a hard-plastic disk.

optical disks
To read the data, a lowpowered laser light scans the disk surface: pitted areas are not reflected and are interpreted as 0 bits; smooth areas are reflected and are interpreted as 1 bit.

Optical disk types (p4.19-p4.24)
CD-ROM disks CD-R disks
– WORM

CD-RW disks
– Erasable CD

DVD/DVD-ROM

4.6 the importance of backup(p4.25)
backup is the name given to tapes, diskettes, or disks that store copies of programs and data stored elsewhere. remember to keep the backup media in a different place.

4.7 other forms of secondary storage (p4.25-p4.26)
flash-memory cards
– flash-memory cards have no moving parts. – consist of circuitry on credit-cardsize cards that can be inserted into slots connecting to the motherboard. – can hold up to 100 MB of data.

flash-memory cards

other forms of secondary storage
Key chain hard drives 钥匙链硬盘驱动器 – Also known as key chain flash memory devices – Are so compact that they can be transported on a key ring or a necklace. – Connect directly to a computer’s USB port

About USB flash drive

USB flash drive
USB flash drive consists of flash memory data storage device integrated with a USB (Universal Serial Bus) 1.1 or 2.0 interface. USB flash drives are typically removable and rewritable, much smaller than a floppy disk, and most weigh less than 1 ounce (30 g).

USB flash drive
Storage capacities can range from 16 MB to 256 GB with steady improvements in size and price per capacity. Some allow 1 million write or erase cycles and have 10-year data retention.

USB flash drive
USB flash drives are often used for the same purposes as floppy disks were. They are smaller, faster, have thousands of times more capacity, and are more durable and reliable due to their lack of moving parts.

USB flash drive
Until approximately 2005, most PC and laptop computers were supplied with floppy disc drives, but most recent equipment has abandoned floppy disk drives in favor of USB ports.

USB flash drive
Flash drives use the USB mass storage standard, supported natively by modern operating systems such as Windows, Mac OS X, Linux, and other Unix-like systems.

USB flash drive
USB drives with USB 2.0 support can store more data and transfer faster than a much larger optical disc drive and can be read by most other systems such as the Microsoft Xbox 360.

homework
1. important new words. 2. translations.

Translation-1(p4.6)

Program files contain software instructions . Source program files contain high level computer instructions in their original form ,as written by the programmers .These instructions must be translated into machine language instructions in order for the processor to use them .The files that contain the machine language instructions are called executable files.

Translation-2 (p4.6)

A file name consists of a unique name, which describes its contents ,and a three-character extension, which describes its type.

Translation -3 (p4.11)
Formatting, or initializing, means preparing the disk so that the computer’s operating system software can write information on it. This includes defining the tracks and sectors on it, as well as setting up the FAT.


相关文章:
更多相关标签: