The fourth generation of computers is more difficult to define than the other three generations. This generation is characterized by more and more transistors being contained on a silicon chip. First there was Large Scale Integration (LSI), with hundreds and thousands of transistors per chip, then came Very Large Scale Integration (VLSI),with tens of thousands and hundreds of thousands of transistors. The trend continues today.第四代计算机比其他三代更难以定义。这一代计算机的特征是一个芯片上包含越来越多的晶体管。首先，出现了一个芯片上具有数百和数千个晶体管的大规模集成电路(LSI)，接着出现了一个芯片上具有数万和数十万个晶体管的超大规模集成电路(VLSI)。这个趋势在今天仍在持续。
Although not everyone agrees that there is a fourth computer generation, those that do feel that it began in 1971, when IBM introduced its successors to the System/360 line of computers. These mainframe computers were called the System/370,and current-modelIBM computers, although not called System/370s,evolved directly from these computers.虽然并不是每个人都同意存在一个第四代,那些认为存在的觉得它开始于1971年，其时IBM开发了System/360系列计算机的下一系列产品。这些大型计算机称为System/370,当前的IBM计算机虽然不叫做System/370，但都是从这些计算机直接发展而来的。
Minicomputers also proliferated during the fourth computer generation. The most popular lines were the DEC PDP-11 models and the DEC VAX,both of which are available in various models today.小型计算机也在第四代期间迅速增长。最流行的系列是DEC公司的PDP-11机和DEC的VAX机,二者在今天的各种机型中仍然有效。
Supercomputers first became prominent in the fourth generation. Although many companies, including IBM and CDC, developed high-speed computers for scientific work, it was not until Cray Research, Inc., introduced the Cray1 in 1975 that supercomputers became significant. Today, supercomputers are an important computer classification. 超级计算机首先在第四代中突起。虽然包括IBM和CDC(控制数据公司)在内的许多公司都为科学工作开发了高速计算机,但是直到1975年Cray研究有限公司推出了Cray1，超级计算机才变得有意义。今天，超级计算机是重要的计算机分类。
Perhaps the most important trend that began in the fourth generation is the proliferationof microcomputers. As more and more transistors were put on silicon chips, it eventually became possible to put an entire computer processor, called a microprocessor, on a chip. The first computer to use microprocessors became available in the mid-1970s. The first microcomputer designed for personal use was the Altair, which was sold in 1975. The first Apple computer, marketed with the IBM PC in 1981. Today, microcomputers far outnumber all other types of computers combined. 也许在第四代计算机开始的最重要趋势是微型计算机的增长。随着越来越多的晶体管被集成到硅芯片上,将一整个计算机处理器（称为微处理器）放在一个芯片上终于成为可能。使用微处理器的第一部计算机出现于1970年代。第一部专为个人使用设计的微型计算机是Altair,它于1975进入市场。第一部苹果计算机在1981年与IBM个人计算机一起在市场上销售。今天，微型计算机数目远远超过其他所有类型计算机的总和。
Software development during the fourth computer generation started off with little change from the third generation. Operating systems were gradually improved, and new languages were designed. Database software became widely used during this time. The most important trend, however, resulted from the microcomputer revolution. Packaged software became widely available for microcomputers so that today most software is purchased, not developed from scratch.在计算机的第四代期间，软件的发展开始与第三代有所不同。操作系统在逐渐地改进，而新的语言被发明。期间数据库软件被广泛使用。然而，最重要的趋势起因于微型计算机革命。用于微型计算机的软件包随处可得，因此今天大多数的软件可以购得,而不需从头开始开发。
We may have defined our last generation of computers and begun the era of generationless computers. Even though computer manufacturers talk of “fifth” and “sixth”-generation computers, this talk is more a marketing play than a reflection of reality.我们可能已经定义了我们最新一代计算机而且开始了计算机的无代时代。即使计算机制造商谈到“第五”和“第六”代计算机,这些说法更多是市场行为，而不是真实的反映。
Advocates of the concept of generationless computers say that even though technological innovations are coming in rapid succession,no single innovation is,or will be, significant enough to characterize another generation of computers.无代计算机的观念提倡者说，即使科技革新接二连三地迅速出现,没有一种革新是,或将是足够重要，作为另一代计算机的特征。
如果您需要翻译，请拨打400 688 3621或者发邮件至alice.han@translationinchina.com,或访问至尚翻译公司网址：http://www.translationinchina.com
Should you need our service, please feel free to call 400 688 3621 or send email to:alice.han@translationinchina.com or visit SIS Shanghai Translation Company Website http://www.translationinchina.com