Chapter-2--Computer-System-Maintenance(計算機系統(tǒng)維護)

1、朱龍 劉長君 主編孫雅妮 謝宇 副主編趙克林 主審工業(yè)和信息化“十三五”高職高專人才培養(yǎng)規(guī)劃教材教學要求： 本章是計算機維護的必備知識，要求學生對硬件已有了解。教學內容： 開機全過程，CMOS，設備添加、刪除與配置，常用DOS命令與網(wǎng)絡命令。教學提示： 建議到機房上課，特別是DOS命令和網(wǎng)絡命令，通過練習才能掌握。ChapterComputer System Maintenance （計算機系統(tǒng)維護）2.1 Booting the Computer（啟動計算機）Whenever you turn on your computer, the first thing you see is the

2、BIOS（Basic Input/Output System）software which is running. On many mach- ines, the BIOS displays text describing things like the amount of memory installed in your computer, the type of hard disk and so on. It turns out that, during this booting, the BIOS is doing a remarkable amount of work to get y

3、our computer ready to run. This section briefly describes some of those activities for a typical PC.啟動計算機，你所看到的第一件事就是BIOS（基本輸入輸出系統(tǒng)）軟件正在執(zhí)行它的操作。在許多計算機上，BIOS會顯示出文字描述信息，比如計算機內存容量、硬盤類型等。這意味著在啟動的程序中BIOS正在進行大量的工作以使你的計算機做好運行前的準備。這一節(jié)我們以常見的計算機為例簡要地介紹計算機的啟動過程。Boot the Computer Key words: BIOS（基本輸入輸出系統(tǒng)），install

4、（安裝，安置），boot（啟動），remarkable（不同尋常的），briefly（暫時地，簡要地）After checking the CMOS Setup and loading the interrupt handlers, the BIOS determines whether the video card is operational. Most video cards have a miniature BIOS of their own that initializes the memory and graphics processor on the card. If they

5、do not, there is usually video driver information on another ROM on the motherboard that the BIOS can load.檢查CMOS設置、載入中斷處理程序后，BIOS檢測顯卡是否工作。大多數(shù)的顯卡都自帶有微型BIOS來初始化顯卡上的顯存和圖形處理器。如果顯卡沒有自帶BIOS，通常在主板的另一個只讀存儲器中會存有BIOS能夠載入的顯卡驅動程序。Next, the BIOS checks to see if this is a cold boot or a reboot. It does this by

6、checking the value at memory address 0000:0472. A value of 1234h indicates a reboot, and the BIOS skips the rest of POST. Anything else is considered a cold boot.If it is a cold boot, the BIOS verifies RAM by performing a read/write test of each memory address. It checks the PS/2 ports or USB ports

7、for a keyboard and a mouse. It looks for a peripheral component interconnect (PCI) bus. If it finds one, it checks all the PCI cards. If the BIOS finds any errors during the POST, it will notify you by a series of beeps or a text message displayed on the screen. An error at this point is almost alwa

8、ys a hardware problem.The BIOS then displays some details about your system. This typically includes information about:The processorThe floppy driver and hard driverMemoryBIOS revision and date DisplayAny special drivers, such as the ones for small computer system interface (SCSI) adapters, are load

9、ed from the adapter, and the BIOS displays the information. The BIOS then looks at the sequence of storage devices identified as boot devices in the CMOS Setup.緊接著，BIOS通過檢測內存地址0000:0472中的值來檢查此次啟動是冷啟動還是熱啟動。若該內存地址中的值為1234h表示熱啟動，則BIOS將跳過剩下的加電自檢程序。檢測到任何其他的值BIOS都將認為此次啟動是冷啟動。如果是冷啟動，BIOS通過對每個內存地址進行讀寫測試來校驗隨

10、機存儲器。BIOS檢查鍵盤和鼠標的PS/2端口或者USB端口。然后BIOS查找互連外圍設備（PCI）總線。如果它找到一個，則檢測所有的PCI卡。如果BIOS在執(zhí)行自檢程序過程中發(fā)現(xiàn)任何錯誤，則會通過一系列的鳴叫聲或在屏幕上顯示文字信息來提示你。此時的錯誤幾乎都是硬件方面的問題。接下來，BIOS通常會顯示系統(tǒng)的一些詳細信息。主要信息包括處理器軟盤驅動器和硬盤驅動器內存BIOS版本和日期顯示器任何特殊驅動程序都從適配器載入，BIOS會顯示出相關信息，比如小型計算機系統(tǒng)接口（SCSI）適配器的驅動程序就是如此。之后，BIOS查看CMOS設置中的啟動設備，也就是存儲設備的順序。 Key words:

11、CMOS（互補金屬氧化物半導體），interrupt handlers（中斷處理程序），miniature（微型的），graphic（圖形的），ROM（只讀存儲器），POST（加電自檢程序），RAM（隨機存儲器），USB（通用串型總線），peripheral（外圍的），component（成分），interconnect（使互相連接），PCI（互連外圍設備），interface（接口），SCSI（小型計算機系統(tǒng)接口），adapter（適配器）NotesPS/2: A lot of brand machines use PS/2 interface to connect the mouse an

12、d keyboard. The PS/2 interface is different from the traditional keyboard interface in the interface appearance and pins, while in data transfer format they are the same. Now many motherboard with the PS/2 interface socket is connected with the keyboard. The keyboard can be achieved by traditional i

13、nterface PS/2 interface converter connected to the motherboard PS/2 interface socket. 很多品牌機上采用PS/2接口來連接鼠標和鍵盤。PS/2接口與傳統(tǒng)的鍵盤接口在接口外形和引腳是不同的，然而在數(shù)據(jù)傳送格式上是相同的?，F(xiàn)在很多主板用PS/2接口插座連接鍵盤，傳統(tǒng)接口的鍵盤可以通過PS/2接口轉換器連接主板PS/2接口插座。details about your computer system“Boot” is short for “bootstrap”, as in an old saying, “Lift yo

14、urself up by your bootstraps”. Boot refers to the process of launching the operating system. The BIOS will try to initiate the boot sequence from the first device. If the BIOS does not find a device, it will try the next device in the list. If it does not find the proper files on a device, the start

15、up process will halt. If you have ever left a floppy disk in the drive when you restarted your computer, you have probably seen this message.The BIOS has tried to boot the computer with ignoring the floppy disk left in the drive. Since it cannot find the correct system files, it can not continue. Of

16、 course, this is an easy fix. Simply take out the disk and press a key to continue.Boot是Bootstrap（自舉程序）的簡略形式，正如古語所說，“拎著鞋帶把自己提起來”。我們用Boot來代表啟動操作系統(tǒng)的過程。BIOS會從第一個啟動設備開始這個啟動過程。如果BOIS沒有找到第一個啟動設備，則會使用列表中的下一個設備嘗試啟動。如果它沒有找到有關設備的正確文件，啟動過程將會暫停。如果你在重新啟動計算機時曾把軟盤留在軟盤驅動器中，你可能就見過這種暫停信息。BIOS試圖不考慮驅動器中軟盤的影響繼續(xù)啟動計算機，但由于

17、它無法找到正確的系統(tǒng)文件，所以無法繼續(xù)啟動。當然，這情況很容易處理，只需取出磁盤，按下任意鍵就可以繼續(xù)啟動。 Key words: bootstrap（自舉程序），Lift yourself up by your bootstraps（自舉），ignore（忽視），floppy disk（軟盤）This is the message you get if a floppy disk is in the drive when you restart your computer.2.2 Basic Input and Output System （基本輸入輸出系統(tǒng)）2.2.1 What Is BI

18、OS（什么是BIOS）The BIOS, pronounced “bye-ose”, is a special software that interfaces the major hardware com- ponents of your computer with the operating system. It is usually stored on a Flash Memory chip on the motherboard, but sometimes the chip is another type of ROM.BIOS發(fā)音為“bye-ose”，它是用來連接計算機主要硬件部分和

19、操作系統(tǒng)的一種特殊軟件。通常，BIOS程序儲存在主板上的一塊閃存芯片中，但有時候也可能是用另一種類型的只讀存儲器作為其存儲芯片。On virtually every computer available, the BIOS makes sure all the other chips, hard drives, ports and CPU function together.Every desktop and laptop computer in common use today contains a microprocessor as its central processing unit.

20、 The microprocessor is the hardware component. To get its work done, the microprocessor executes a set of instructions known as software. You are probably very familiar with two different types of software: the operating system and the applications.It turns out that the BIOS is the third type of sof

21、tware your computer needs to operate successfully. In this part, youll learn all about BIOSwhat it does, and how to configure it.事實上，對于每臺可用的計算機，BIOS程序是用來確保所有的其他芯片、硬件驅動器、端口和CPU能夠協(xié)同工作的。如今，每臺公用臺式和便攜式計算機都使用微處理器作為其中央處理器。微處理器屬于硬件。為了使它正常工作，微處理器需要執(zhí)行一系列被稱為“軟件”的指令。你可能對兩種類型的軟件很熟悉：操作系統(tǒng)和應用軟件。很顯然，BIOS就是使你的計算機能夠順利

22、工作所必需的第三種類型的軟件。在這一節(jié)，你將會學習BIOS的相關知識BIOS做些什么以及如何配置它。Inside the above-mentioned ROM three different programs are stored (actually burned). The Basic Input and Output System (BIOS) that is responsible for teaching the main processor how to deal with basic devices, such as floppy unit or hard disk and so

23、 on; the Power on Self Test (POST) which is the program in charge of the self test that is executed every time PC is powered up (like memory counting, for instance); and the Setup which is the program that allows the alteration of the parameters stored in the configuration memory (CMOS).在上述只讀存儲器中存儲著

24、三種不同類型的程序（事實上是燒錄上去的）?；镜妮斎胼敵鱿到y(tǒng)（BIOS程序）負責指導主處理器如何控制像軟盤驅動器、硬盤之類的基本設備。加電自檢程序（POST）是負責在每次計算機開機時執(zhí)行自檢測的程序（比如內存容量檢測）。設置程序（Setup）則是種專門用來修改CMOS中存儲參數(shù)的程序。 Key words: Flash Memory（閃速存儲器），CPU（中央處理器），microprocessor（微處理器），PC（個人計算機），Setup（設置程序），Configuration Memory（CMOS設置存儲器）Phoenix BIOSAMI BIOS2.2.2 What BIOS Does

25、（BIOS的任務是什么）The BIOS software has a number of different roles, but its most important role is to load the operating system. When you turn on your computer and the microprocessor tries to execute its first instruction, it has to get that instruction from somewhere. It cannot get it from the operating

26、 system because the operating system is located on a hard disk, and the microprocessor cannot get to it without some instructions that tell it how. The BIOS provides those instructions.BIOS軟件要執(zhí)行許多不同的任務，但最重要的任務是載入操作系統(tǒng)。當你打開計算機時，微處理器嘗試執(zhí)行第一條指令，它必須從某個地方獲取該指令。但由于操作系統(tǒng)存儲在硬盤上，微處理器不可能在沒有指令的情況下執(zhí)行讀取指令的操作，所以微處理器

27、無法從操作系統(tǒng)中獲得第一條指令。BIOS就提供了那些指令。Some of the other common tasks that the BIOS performs include:A power on Self Test (POST) for all of the different hardware components in the system to make sure everything is working properly.Activating other BIOS chips on different cards installed in the computerFor ex

28、ample, SCSI and graphics cards often have their own BIOS chips.BOIS需要執(zhí)行的其他任務如下。對計算機系統(tǒng)中所有不同的硬件部分進行加電自檢（POST），確定所有設備工作正常。激活計算機中其他硬件卡上的BIOS芯片例如，SCSI卡和圖形卡通常都有自己的BIOS芯片。Providing a set of low-level routines that the operating system uses to interface to different hardware devicesIt is these routines that

29、 give the BIOS its name. They manage things like the keyboard, the screen, and the serial and parallel ports, especially when the computer is booting. Managing a collection of settings for the hard disks, clock, etc.When you turn on your computer, the BIOS performs the following tasks. This is its u

30、sual sequence: 1Check the CMOS Setup for custom settings 2Load the interrupt handlers and device drivers 3Initialize registers and power management 4Perform the Power on Self Test (POST) 5Display system settings6Determine which devices are bootable 7Initiate the bootstrap sequence The first thing th

31、e BIOS does is checking the information stored in a tiny (64 bytes) amount of RAM located on a complementary metal oxide semiconductor (CMOS) chip. The CMOS Setup provides detailed information particular to your system and can be altered as your system changes. The BIOS uses this information to modi

32、fy or supplement its default programming as needed.提供一系列低級別程序連接操作系統(tǒng)和不同的硬件設備BIOS正是因為這些程序而得名。這些程序可以管理各種設備，諸如鍵盤、屏幕、串口和并口，尤其是在計算機啟動的時候。管理硬盤、時鐘等的設置。當你啟動計算機時，BIOS就執(zhí)行如下幾項任務，并通常按下列順序執(zhí)行。1檢測CMOS常規(guī)設置；2載入中斷處理程序和設備驅動程序；3初始化寄存器和電源管理；4執(zhí)行加電自檢程序（POST）；5顯示系統(tǒng)設置；6確定可啟動設備；7開始自舉程序。BIOS所做的第一件事情是檢查CMOS芯片上微?。?4字節(jié)）的隨機存儲器中存儲的

33、信息。CMOS設置程序提供了關于你的計算機系統(tǒng)的詳細信息，隨著系統(tǒng)改變，CMOS設置也能夠被修改。BIOS使用這些信息來修改或補充所需要的默認程序。 Key words: CMOS Setup（CMOS設置程序），complementary metal oxide semiconductor（互補金屬氧化物半導體）2.2.3 Configuring BIOS（設置BIOS）In the previous list, you saw that the BIOS checks the CMOS Setup for common settings. Heres what you do to chan

34、ge those settings. To enter the CMOS Setup, you must press a certain key or combination of keys during the initial startup sequence. Most systems use “Esc,” “Del,” “F1,” “F2,” “Ctrl-Esc” or “Ctrl-Alt-Esc” to enter setup. There is usually a line of text at the bottom of the display that tells you “Pr

35、ess _ to enter setup.”在前面的列表中，你可以看到BIOS檢測CMOS中的設置來作為計算機的常規(guī)設置。這里我們將介紹你如何改變這些設置。要進入CMOS設置界面，你必須在計算機最初啟動的時候按下一個特定按鍵或者組合按鍵。大多數(shù)的系統(tǒng)使用“Esc”“Del”“F1”“F2”“Ctrl-Esc”或者“Ctrl-Alt-Esc”按鍵來進入CMOS的設置界面。通常，屏幕下方會顯示一行文字提示用戶“按下_鍵進入設置界面”。Once you have entered setup, you will see a set of text screens with a number of op

36、tions. Some of these are standard, while others vary according to the BIOS manufacturer. Common options include:InformationSomething about the computers informationBIOS VersionThe version number of BIOS一旦你進入了設置界面，你將會看到包含一系列文字選項信息的屏幕。有些選項是標準的，而其他選項可能會根據(jù)BIOS制造商的不同而不同。一般的選項都包括如下各項。信息顯示關于電腦的信息；BIOS版本顯示B

37、IOS的版本號；System Time/DateSet the system time and date Boot PriorityThe order that BIOS will try to load the operating systemPlug and PlayA standard for autodetecting connected devices should be set to “Yes” if your computer and operating system both support it Mouse/Keyboard“Enable Num Lock” “En- abl

38、e the Keyboard” “Auto-Detect Mouse”. Drive ConfigurationConfigure hard drives, CD-ROM and floppy drives MemoryDirect the BIOS to shadow to a specific memory address SecuritySet a password for accessing the computer Power ManagementSelect whether to use power management, as well as set the amount of

39、time for standby and suspend ExitSave your changes, discard your changes or restore default settings系統(tǒng)時間/日期設置系統(tǒng)時間和日期；啟動順序設置BIOS載入操作系統(tǒng)的順序；即插即用設備自動檢測連接設備的標準，如果計算機和操作系統(tǒng)都支持自動檢測連接的設備，應該將其設置為“Yes”；鼠標/鍵盤“啟用數(shù)字鍵”“啟用鍵盤”“自動檢測鼠標”驅動器設置設置硬盤驅動器、只讀光盤和軟盤驅動器；內存可命令BIOS將特定的內存地址指定為影子內存使用；安全性設置訪問計算機的密碼；電源管理選擇是否使用電源管理，設置待

40、命和掛機的時間；退出保存用戶設置，放棄用戶設置或者恢復默認設置。Award CMOS設置界面Phoenix CMOS設置界面Be very careful when making changes to setup. Incorrect settings may keep your computer from booting. When you finish with your changes, you should choose “Save Changes” and exit. The BIOS will then restart your computer so that the new s

41、ettings take effect.當改變CMOS設置時要很小心，錯誤的設置可能使你的計算機無法啟動。當你完成了更改設置，你應該選擇“保存設置”然后退出。BIOS將會重新啟動計算機從而使新的設置起效。AMI CMOS設置界面 Key words: manufacturer（制造商），Pluy and Play（即插即用），Shadow Memory（影子內存），security（安全性），standby（待機），suspend（暫停、掛起），exit（退出）2.2.4 What Is CMOS（什么是CMOS）Pronounced see-moss, CMOS (Short for com

42、plementary metal oxide semiconductor) is a special kind of memory maintained by a small battery after you turn the computer off. The BIOS uses CMOS memory to store the settings you select in Setup and to maintain the internal real time clock (RTC). A small lithium or Ni-Cad battery can supply enough

43、 power to CMOS to keep the data for years. Every time you turn on your computer, the BIOS uses the CMOS settings to configure your computer. If the battery charge runs too low, the CMOS contents will be lost and POST will issue a “CMOS invalid” or “CMOS checksum invalid” message. If it happens, you

44、may have to replace the battery. After the battery is replaced, the proper settings will need to be restored in Setup.讀作“see-moss”的CMOS（互補金屬氧化物半導體的縮寫）是一種在計算機斷電后還能夠由小型電池供電的低功耗存儲器。BIOS使用CMOS存儲器來存儲用戶在設置程序（Setup）中進行的設置，同時保持計算機內部的實時時鐘（RTC）。使用一塊很小的鋰電池或鎳鎘電池就可以為CMOS供電數(shù)年之久，以保存數(shù)據(jù)。每次當用戶啟動計算機時，BIOS使用CMOS中存儲的設置來

45、配置你的計算機。如果電池供電不足，CMOS中的內容將會丟失，同時自檢程序將會提示“CMOS錯誤”或者“CMOS校驗錯誤”的信息。如果這種情況發(fā)生，你必須更換電池。更換電池后，需要在設置界面中重新存儲相應的設置信息。 Key words: Semiconductor（半導體），RTC（實時時鐘），Setup（設置程序或設置界面）2.2.5 What Is POST（什么是POST）POST is an acronym for Power on Self Test. When a personal computer is firstly turned on, the BIOS tests and

46、configures various components to ensure that they are operating correctly. This operation is called POST (Power on Self Test).Its meaning includes anything the BIOS does before an operating system is started.If the BIOS detects any problems during the POST, it will attempt to continue to start the c

47、omputer. However, if the problems are serious, the BIOS may be forced to halt the system.When an error is detected, the BIOS program will:Display the error to the screen if possible. Generate a POST beep code using the computers internal speaker if it cannot access the display adaptor. Provide a POS

48、T Code output that can be read by using a special hardware tool.POST是加電自檢的縮寫。當個人計算機最初啟動時，BIOS檢測和配置各種組件以確保它們正常工作。這個操作就叫作自檢（加電自檢）。自檢程序包括啟動操作系統(tǒng)之前BIOS所進行的所有工作。在檢測過程中，如果BIOS檢測到任何問題，它將試圖繼續(xù)啟動計算機。但是，如果問題嚴重，BIOS可能被迫使系統(tǒng)暫停。當檢測到錯誤時，BIOS程序將會：盡可能在屏幕上顯示錯誤信息。如果無法訪問顯示器，它會使用計算機內部的揚聲器發(fā)出自檢鳴叫聲。輸出一個自檢代碼，可以通過特定的硬件工具來讀取該代碼

49、。 Key words: acronym（只取首字母的縮寫詞），POST beep code（自檢鳴叫錯誤），POST Code（自檢代碼）Next, we will use Award BIOS error messages to introduce the important information about beep codes and screen error messages during POST.Beep CodesThe only Award BIOS beep code indicates that a video error has occurred and the BI

50、OS cannot initialize the video screen to display any additional information. This beep code consists of a single long beep followed by two short beeps. Any other beeps are probably a RAM (Random Access Memory) problem.Screen Error MessagesThe following messages are examples of messages including err

51、ors detected by the BIOS during POST and a description of what they mean and/or what you may do to correct the error.BIOS ROM checksum errorSystem halted The checksum of the BIOS code in the BIOS chip is incorrect, indicating the BIOS code may have become corrupt. Contact your system dealer to repla

52、ce the BIOS.CMOS battery failed The CMOS battery is no longer functional. Contact your system dealer for a battery replacement.CMOS checksum errorDefaults loadedChecksum of CMOS is incorrect, so the system loads the default equipment configuration. A checksum error may indicate that CMOS has become

53、corrupt. This error may have been caused by a weak battery. Check the battery and replace if necessary.下面，我們以Award BIOS的錯誤信息提示為例介紹在自檢過程中有關鳴叫聲和屏幕錯誤信息的重要內容。鳴叫代碼當有顯示故障發(fā)生時，Award BIOS只能發(fā)出鳴叫聲提示錯誤信息，而不能初始化顯示屏來顯示任何附加信息。這種鳴叫聲由一聲長鳴緊接著兩聲短鳴構成。其他的鳴叫類型可能是提示隨機存儲器故障。屏幕錯誤信息下面的信息示例是些在自檢過程中BIOS檢測到的錯誤信息及其含義和用戶可以進行的相應處理

54、措施。BIOS校驗錯誤系統(tǒng)暫停BIOS芯片中的BIOS代碼檢測錯誤，意味著BIOS代碼可能已經(jīng)被破壞。用戶需要和計算機系統(tǒng)經(jīng)銷商聯(lián)系更換BIOS芯片。CMOS電池失效CMOS電池不再有效。用戶需要聯(lián)系系統(tǒng)經(jīng)銷商更換CMOS電池。CMOS校驗錯誤載入默認設置CMOS校驗錯誤，于是系統(tǒng)載入默認的設備配置。校驗錯誤可能表示CMOS信息被破壞。發(fā)生這種錯誤的原因可能是電池電量不足，如果必要的話可以先更換電池。Display switch is set incorrectlyThe display switch on the motherboard can be set to either monoch

55、rome or color. This message indicates the switch is set to a different setting than indicated in Setup. Determine which setting is correct, and then either turn off the system and change the jumper, or enter Setup and change the VIDEO selection.Press Esc to skip memory test The user may press Esc to

56、 skip the full memory test.Floppy disk(s) fail Cannot find or initialize the floppy drive controller or the drive. Make sure the controller is installed correctly. If no floppy drives are installed, be sure the Diskette Drive selection in Setup is set to NONE or AUTO.Hard disk initializingPlease wai

57、t a moment Some hard drives require extra time to initialize.Hard disk install failures Cannot find or initialize the hard drive controller or the drive. Make sure the controller is installed correctly. If no hard drives are installed, be sure the Hard Drive selection in Setup is set to NONE.Hard di

58、sk(s) diagnosis fail The system may run specific disk diagnostic routines. This message appears if one or more hard disks return to an error when the diagnostics run.顯示開關設置錯誤主板上的顯示開關可以設置為單色或彩色。這條錯誤信息表示開關的設置與CMOS中的設置不相符。首先確定哪一個設置是正確的，然后關閉系統(tǒng)改變跳線或者進入CMOS設置界面更改“顯示”選項。按下Esc鍵跳過內存檢測用戶可以按下ESC鍵跳過完整的內存檢測。軟盤驅動

59、器驅動失敗無法找到或初始化軟盤驅動控制器或驅動器。用戶需要確定控制器安裝是否正確。如果沒有安裝軟盤驅動器，則要將設置界面中的“磁盤驅動器選擇”選項設置為“無”或是“自動”。硬盤正在初始化請稍候有些硬盤啟動器需要額外的時間來初始化。硬盤安裝失敗無法找到或初始化硬盤驅動控制器或驅動器。用戶需要確定控制器安裝是否正確。如果沒有安裝硬盤驅動器，則要將設置界面中的“硬盤選擇”選項設置為“無”。執(zhí)行硬盤診斷時發(fā)生錯誤系統(tǒng)可以運行特定的硬盤診斷程序。當診斷程序運行時，如果一個或多個硬盤返回錯誤，屏幕上就會顯示這條信息。Keyboard error or no keyboard present Cannot

60、initialize the keyboard. Make sure the keyboard is attached correctly and no keys are pressed during POST. To purposely configure the system without a keyboard, set “the error halt condition” in Setup to “halt on all, but keyboard”. The BIOS then ignores the missing keyboard during POST.Keyboard is