Now that we have looked below your program to uncover the underlying software, let‘s open the covers of your computer to learn about the underlying hardware. The underlying hardware in any computer performs the same basic functions: inputting data, outputting data, processing data, and storing data. How these functions are performed is the primary topic of this book, and subsequent chapters deal with different parts of these four tasks.
When we come to an important point in this book, a point so important that we hope you will remember it forever, we emphasize it by identifying it as a Big picture item. We have about a dozen Big Pictures in this book, the first being the five components of a computer that perform the tasks of inputting, outputting processing, and storing data.
Two key components of computers are input devices, such as the microphone, and output devices, such as the speaker. As the names suggest, input feeds the computer, and output is the result of computation sent to the user. Some devices such as wireless networks, provide both input and output to the computer.
Chapters 5 and 6 describe input/output (I/O) devices in more detail, but let‘s take an introductory tour through the computer hardware, starting with the external I/O devices.
The five classic components of a computer are input, memory, datapath, and control, with the last two sometimes combined and called the processor. Figure 1.5 shows the standard organization of a computer. This organization is independent of hardware technology: you can place every piece of every computer, past and present, into one of these five categories. To help you keep all this in perspective, the five components of a copmputer are shown on the front page of each of the following chapters, with the portion of interest to that chapter highlighted.
Through the looking glass
The most fascinating I/O device is probably the graphics display. Most personal mobile devices use liquid crystal display (LCDs) to get a thin, low-power display. The LCD is not the source of light; instead, it controls the transmission of light. A typical LCD includes rod-shaped molecules in a liquid that form a twisting helix that bends light entering the display, from either a light source behind the display or less often from reflected light. The road straighten out when a current is applied or less often from reflected light. Since the liquid crystal material is between two screens polarized at 90 degrees, the light can not pass through unless it is bent. Today, most LCD displays use an active matrix that has a tiny transistor switch at each piex to precisely control current and make sharper images. A red-green-blue mask associated with each dot on the display determines the intensity of the three-color components in the final image; in a color active matrix LCD, there are three transistor switches at eah point.
The image is composed of a matrix of picture elements, or pixels, which can be represented as a matrix of bits, called a bit map.
原文：http://www.cnblogs.com/666638zhangqiang/p/4989041.html