2.1　Booting the Computer（启动计算机）

Whenever you turn on your computer, the first thing you see is the BIOS（Basic Input/Output System）software which is running. On many machines, 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 your computer ready to run.This section briefly describes some of those activities for a typical PC.

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 do not, there is usually video driver information on another ROM on the motherboard that the BIOS can load.

Next, the BIOS checks to see if this is a cold boot or a reboot. It does this by 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 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 always a hardware problem.

The BIOS then displays some details about your system. This typically includes information about:

·The processor

·The floppy driver and hard driver

·Memory

·BIOS revision and date

·Display

Any special drivers, such as the ones for small computer system interface (SCSI) adapters, are loaded 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.

启动计算机，你所看到的第一件事就是BIOS（基本输入输出系统）软件正在执行它的操作。在许多计算机上，BIOS会显示出文字描述信息，比如计算机内存容量、硬盘类型等。这意味着在启动的程序中BIOS正在进行大量的工作以使你的计算机做好运行前的准备。这一节我们以常见的计算机为例简要地介绍计算机的启动过程。

检查CMOS设置、载入中断处理程序后，BIOS检测显卡是否工作。大多数的显卡都自带有微型BIOS来初始化显卡上的显存和图形处理器。如果显卡没有自带BIOS，通常在主板的另一个只读存储器中会存有BIOS能够载入的显卡驱动程序。

紧接着，BIOS通过检测内存地址0000:0472中的值来检查此次启动是冷启动还是热启动。若该内存地址中的值为1234h表示热启动，则BIOS将跳过剩下的加电自检程序。检测到任何其他的值BIOS都将认为此次启动是冷启动。

如果是冷启动，BIOS通过对每个内存地址进行读写测试来校验随机存储器。BIOS检查键盘和鼠标的PS/2端口或者USB端口。然后BIOS查找互连外围设备（PCI）总线。如果它找到一个，则检测所有的PCI卡。如果BIOS在执行自检程序过程中发现任何错误，则会通过一系列的鸣叫声或在屏幕上显示文字信息来提示你。此时的错误几乎都是硬件方面的问题。

接下来，BIOS通常会显示系统的一些详细信息。主要信息包括

·处理器

·软盘驱动器和硬盘驱动器

·内存

·BIOS版本和日期

·显示器

任何特殊驱动程序都从适配器载入，BIOS会显示出相关信息，比如小型计算机系统接口（SCSI）适配器的驱动程序就是如此。之后，BIOS查看CMOS设置中的启动设备，也就是存储设备的顺序。

Boot the Computer

Key words： BIOS（基本输入输出系统），install（安装，安置），boot（启动），remarkable（不同寻常的），briefly（暂时地，简要地）

Key words：CMOS（互补金属氧化物半导体），interrupt handlers（中断处理程序），miniature（微型的），graphic（图形的），ROM（只读存储器），POST（加电自检程序），RAM（随机存储器），USB（通用串型总线），peripheral（外围的），component（成分），interconnect（使互相连接），PCI（互连外围设备），interface（接口），SCSI（小型计算机系统接口），adapter（适配器）

Notes

PS/2: A lot of brand machines use PS/2 interface to connect the mouse and 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 interface PS/2 interface converter connected to the motherboard PS/2 interface socket. 很多品牌机上采用PS/2接口来连接鼠标和键盘。PS/2接口与传统的键盘接口在接口外形和引脚是不同的，然而在数据传送格式上是相同的。现在很多主板用PS/2接口插座连接键盘，传统接口的键盘可以通过PS/2接口转换器连接主板PS/2接口插座。

“Boot” is short for “bootstrap”, as in an old saying, “Lift yourself 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 startup 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 course, this is an easy fix. Simply take out the disk and press a key to continue.

Boot是Bootstrap（自举程序）的简略形式，正如古语所说，“拎着鞋带把自己提起来”。我们用Boot来代表启动操作系统的过程。BIOS会从第一个启动设备开始这个启动过程。如果BOIS没有找到第一个启动设备，则会使用列表中的下一个设备尝试启动。如果它没有找到有关设备的正确文件，启动过程将会暂停。如果你在重新启动计算机时曾把软盘留在软盘驱动器中，你可能就见过这种暂停信息。

BIOS试图不考虑驱动器中软盘的影响继续启动计算机，但由于它无法找到正确的系统文件，所以无法继续启动。当然，这情况很容易处理，只需取出磁盘，按下任意键就可以继续启动。

Key words： bootstrap（自举程序），Lift yourself up by your bootstraps（自举），ignore（忽视），floppy disk（软盘）