《计算机科学导论》课后练习(翻译)(4)

35.根据冯·诺伊曼模型，当今的硬盘可用于输入或输出吗？请解释。

答：The hard disk may be used as either an input device or an output device. When data or programs are read from the disk, the disk is considered an input device. When data or programs are written to the disk, the disk is considered an output device.

硬盘既可作为输入设备，又可作为输出设备。当数据或程序从硬盘中读出时，硬盘被认为是输入设备；当数据或程序被写入硬盘时，硬盘被认为是输出设备。

37.如今，硬件、软件或数据哪一个对组织机构比较有价值？

答：The set of data is the most valuable asset of most organizations. An organization can replace its hardware and software if they are lost (due to theft, fire, etc.) and usually they replace them every few years as hardware or software become obsolete, but the set of data is indispensable.

数据对组织机构来说是最有价值的。硬件和软件如果丢失（被盗、火灾等）组织机构可以替代他们。而且，通常情况下，几年时间硬件和软件就会被淘汰，但是数据却是独一无二的。

Chapter 2

复习题

1.定义一个数字系统。

答：A number system shows how a number can be represented using distinct symbols. 数字系统定义了如何用独特的符号来表示一个数字。

2.辨析位置化和非位置化数字系统。

答：In a positional number system, the position of a symbol determines the value it represents. In a nonpositional number system each symbol has a value but the position of a symbol normally has no relation to its value; the value of each symbol is fixed. 位置化数字系统中，在数字中符号所占据的位置决定了其表示的值。非位置化数字系统仍然使用有限的数字符号，每个符号有一个值。但是符号所占用的位置通常与其值无关——每个符号的值是固定的。

3.定义位置化数字系统中的底或基数。位置化数字化系统中底与符号的数量有关系？

答：The base (or radix) is the total number of symbols used in a positional number system.

位置化数字化系统的底或基数，它是符号集中的符号总数。

4.简述十进制系统。为什么称作decimal?该系统的底是多少？

答：The decimal system is a positional number system that uses ten symbols to represent a number. The word decimal is derived from the Latin root decem (ten) or decimalis (related to ten). In the decimal system, the base is 10.

十进制系统来源于拉丁词根decem（十）。在该系统中，底b=10并且用10个符号来表示一个数。符号集是S={0，1，2，3，4，5，6，7，8，9}。十进制系统中的符号被称为十进制数码或仅称为数码。

5. 简述二进制系统。为什么称作binary?该系统的底是多少？

答：The binary system is a positional number system that uses two symbols (0 and 1) to represent a number. The word binary is derived from the Latin root bini (two by two) or binarius (related to two). In the binary system, the base is 2.

Binary（二进制）来源于拉丁词根bini（二）。在该系统中，底b=2并且用两个符