附文1：Reading Material（阅读材料）

PC Overview

A PC is a small, relatively inexpensive computer designed for an individual user. In price,personal computers range anywhere from a few hundred dollars to over five thousand dollars. All are based on the microprocessor technology that enables manufacturers to put an entire CPU on one chip. Businesses use personal computer for word processing, accounting, desktop publishing,and for running spreadsheet and database management applications. At home, the most popular use for personal computers is for playing games and computer-assisted learning.

Personal computers first appeared in the late 1970s. One of the first and most popular personal computers was the Apple Ⅱ, introduced in 1977 by Apple Computer. During the late 1970s and early 1980s, new models and competing operating systems seemed to appear daily.Then, in 1981, IBM entered the fray (竞争) with its first personal computer, known as the IBM PC, the IBM PC quickly became the personal computer of choice, and most other personal computer manufacturers fell by the wayside. One of the few companies to survive IBM’s onslaught (冲击) was Apple Computer, which remains a major player in the personal computer marketplace.

Other companies adjusted to IBM’s dominance (优势) by building IBM clones, computers that were internally almost the same as the IBM PC, but that cost less. Because IBM clones used the same microprocessors as IBM PCs, they were capable of running the same software. Over the years, IBM has lost much of its influence (影响) in directing the evolution (发展) of PCs. Many of its innovations (创新), such as the MCA ( Micro Channel Architecture) expansion bus and the OS/2 operating system, have not been accepted by the industry or the marketplace.

Today, the world of personal computer is basically divided between Apple Macintoshes and PCs. The principal (主要的) characteristics (特征) of personal computers are that they are single-use systems and are based on microprocessors. However, although personal computers are designed as single-user systems, it is common to link them together to form a network. In terms of power, there is a great variety. At the high end, the distinction between personal computers and workstations has faded (已褪色的). High-end models of the Macintosh and PC offer the same computing power and graphics capability as low-end workstation by Sun Microsystems,Hewlett-Packard, and DEC.

How Do Computers Work?

To accomplish a task using a computer, you need a combination of hardware, software and input.

Hardware consists of devices, like the computer itself, the monitor, keyboard, printer, mouse,and speakers. Inside your computer there are more bits of hardware, including the motherboard,where you would find the main processing chips that make up the central processing unit (CPU).The hardware processes the commands it receives from the software, and performs tasks or calculations.

Software is the name given to the programs that you install on the computer to perform certain types of activities. There is operating system software, such as the Apple OS for a Macintosh, or Windows 95 or Windows 98 for a PC. There is also application software, like the games we play or the tools we use to compose letters or do math problems.

You provide the input. When you type a command or click on an icon, you are telling the computer what to do. That is called input.