1、计 算 概 论 计算机文化、程序设计Introduction to Computing: Computer Culture, and Programming闫宏飞 陈翀 编著by Hongfei Yan and Chong Chen2010/9/23内 容 简 介本书主要是汇编各书和参考资料而成，比较系统地介绍了计算机文化，和程序设计。通过这两部分有机的结合（前者占 1/3，后者占 2/3） ，即理论与实践结合，使学生理解和掌握有关计算机和信息技术的基本概念和基本原理，对计算机学科有全局性的认识；学会使用计算机进行信息处理，熟练掌握 C+语言编程技术，为后续相关课程的学习打好基础。本书层次分明
2、，由浅入深，具有学习和实用双重意义。本书可作为高等院校各专业一、二年级学生的教学参考书和技术资料，对广大从事计算机相关研究和应用开发的科技人员也有很大的参考价值。i前 言计算概论是普通高校面向理工科低年级学生开设的计算机基础教育课。课程前 1/3 部分为计算机文化，后 2/3 部分为程序设计。任教此课两年来，发现没有合适的教材，因此根据授课经验，汇编各书和参考资料，编成此书。编 者2009 年 1 月 于 北 大 燕 园ii目 录前言第 1 章 引论 11.1 计算机科学 21.2 摩尔定律 31.3 SCOPE OF PROBLEMS5上篇 计算机文化 8第 2 章 计算机系统 92.1 C
3、OMPUTER INTRODUCTION 92.1.1 TURING MODEL .102.1.2 VON NEUMANN MODEL 152.1.3 Computer components .172.1.4 History182.1.5 Practice set .212.2 计算机系统漫游 222.1.1 Information is Bits + Context.242.1.2 Programs Are Translated by Other Programs into Different Forms 262.1.3 It Pays to Understand How Compilati
4、on SystemsWork 282.1.4 Processors Read and Interpret Instructions Stored in Memory302.1.5 Caches Matter.362.1.6 Storage Devices Form a Hierarchy 372.1.7 The Operating System Manages the Hardware382.1.8 Systems Communicate With Other Systems Using Networks 452.1.9 The Next Step.472.1.10 Summary 47第 3
5、 章 数据和数的表示 503.1 数据的表示 503.2 数的表示 54iii第 4 章 程序设计语言和开发环境 584.1 程序设计语言 584.2 开发环境 68下篇 程序设计 74第 5 章 C+基础 .755.1 GETTING STARTED .755.2 FUNDAMENTAL TYPES .795.3 ARITHMETIC OPERATOR.815.4 CONTROL STRUCTURES83第 6 章 数组和结构 946.1 数组 946.1.1 Initializing arrays .956.1.2 Accessing the values of an array966.1
6、.3 Multidimensional arrays.976.2 结构 1056.2.1 Data structures1056.2.2 Pointers to structures1096.2.3 Nesting structures.112Quiz : Structures113第 7 章 C+标准库 .1147.1 C LANGUAGE LIBRARY.1157.2 INPUT/OUTPUT STREAM LIBRARY 1167.3 STRING LIBRARY 1177.4 STL: STANDARD TEMPLATE LIBRARY.117第 8 章 函数和递归 1208.1 FU
7、NCTIONS WITH NO TYPE. THE USE OF VOID. .1258.2 ARGUMENTS PASSED BY VALUE AND BY REFERENCE.1278.3 DEFAULT VALUES IN PARAMETERS 1298.4 OVERLOADED FUNCTIONS1308.5 INLINE FUNCTIONS1328.6 RECURSIVITY .1328.7 DECLARING FUNCTIONS .136iv第 9 章 指针和引用 1399.1 POINTERS .1399.1.1 Reference operator ( World Commun
8、ity Grid, an effort to create the worlds largest public computing grid to tackle scientific research projects that benefit humanity, run and funded by IBM; SETIhome, which is focused on analyzing radio-telescope data to find evidence of intelligent signals from space, hosted by the Space Sciences La
9、boratory at the University of California, Berkeley (the Berkeley Open Infrastructure for Network Computing (BOINC), was originally developed to support this project); LHChome, which is used to help design and tune the Large Hadron Collider, hosted by CERN in Geneva; and , which is focused on finding
10、 optimal Golomb rulers and breaking various cryptographic ciphers.http:/folding.stanford.edu/English/Main http:/zh.wikipedia.org/wiki/Foldinghome 第 1 章 引论 6 http:/www.stanford.edu/group/pandegroup/images/FAH-May2008.png http:/ Foldinghome 是如何工作的呢？Foldinghome 是一个研究研究蛋白质折叠，误折，聚合及由此引起的相关疾病的分布式计算工程。使用联网
11、式的计算方式和大量的分布式计算能力来模拟蛋白质折叠的过程，并指引我们近期对由折叠引起的疾病的一系列研究。图 1-3 Foldinghome第 1 章 引论 7 图 1-4 Shrek Dreamworks Animation, rendering multiple frames of high-quality animationHappy Feet Kingdom Feature Productions; Lord of the Rings New Line Cinema 图 1-5 Simulating several hundred or thousand charactersIndexi
12、ng the web (Google)Google（ ）是一个搜索引擎，由两个斯坦福大学博士生Larry Page 与 Sergey Brin 于 1998 年 9 月发明，Google Inc. 于 1999 年创立。Google 网页搜索技术是来源于信息检索技术。Google 的“网页快照”功能，能从Google 服务器里直接取出缓存的网页。Simulating an Internet-sized network for networking experiments (PlanetLab)http:/www.planet-lab.org/ PlanetLab is a global res
13、earch network that supports the development of new network services. Since the beginning of 2003, more than 1,000 researchers at top academic institutions and industrial research labs have used PlanetLab to develop new technologies for distributed storage, network mapping, peer-to-peer systems, dist
14、ributed hash tables, and query processing. PlanetLab currently consists of 1128 nodes at 511 sites. Speeding up content delivery (Akamai)美国 Akamai 是国际上最大的 CDN 服务商,它巨大的网络分发能力在峰值时可达到 15Gbps。Akamai 公司是为数不多的旨在消除 Internet 瓶颈和提高下载速度的几家新公司之一,是一个致力于网络交通提速的“内容发布”公司，是波士顿高技术区最卓越的新兴企业之一。Akamai 公司向全球企业 提供发送互联网内容
15、，汇流媒体和应用程序的服务(目前，该公司为 15 个国家的企业管理着 8000第 1 章 引论 8 多台服务器)。1998 年，丹尼尔 .L 和麻省理工学院的一 些研究人员一起创立了这家公司,他在麻省理工学院的硕士论文构成了 Akamai 公司最初的“自由流”（Freeflow）技术的核心。 9 上篇 计算机文化上篇的主要目的是向读者介绍有关计算机和信息技术的基本概念和基本原理，使读者能够对计算机学科有全局性的认识。第 2 章 计算机系统 10 第 2 章 计算机系统2.1 Computer Introduction本节大部分内容取自下面这本书的第一章。等号线之间内容是我加的。Foundati
16、ons of Computer Science,2e,by Behrouz Forouzan and Firouz Mosharraf, Cengage Learning Business Press, December 5, 2007http:/www.cengage.co.uk/forouzan/ http:/ The phrase computer science has a very broad meaning today. However, in this book, we define the phrase as “issues related to the computer“.
17、This introductory chapter first tries to find out what a computer is, then investigates other issues directly related to computers. We look first at the Turing model as a mathematical and philosophical definition of computation. We then show how todays computers are based on the von Neumann model. T
18、he chapter ends with a brief history of this culture-changing device.the computer.ObjectivesAfter studying this chapter, the students should be able to: Define the Turing model of a computer. Define the von Neumann model of a computer. Describe the three components of a computer: hardware, data, and
19、 software. List topics related to computer hardware. List topics related to data. List topics related to software. Discuss some social and ethical issues related to the use of computers. Give a short history of computers.第 2 章 计算机系统 11 2.1.1 TURING MODELThe idea of a universal computational device w
20、as first described by Alan Turing in 1937. He proposed that all computation could be performed by a special kind of machine, now called a Turing machine. Although Turing presented a mathematical description of such a machine, he was more interested in the philosophical definiton of computation than
21、in building the actual machine. He based the model on the actions that people perform when involved in computation. He abstracted these actions into a model for a computational machine that has really changed the world.Perceptual knowledge (感性认识)计算机组成部分http:/ Introduction to Computer Hardwarehttp:/
22、Install http:/ if your computer can not show videos.图 2-1 Mother board (主板：集成多个部件、适配器，提供它们之间的互联)第 2 章 计算机系统 12 主板(Main Board)又名主机板、系统板、母板，是 PC 机的核心部件。 PC 机的主板包括 CPU、芯片组（ Chipset） 、高速缓存（Cache） 、ROM_BIOS 芯片、CMOS 芯片、内存 RAM、总线通道、软硬磁盘接口、串行和并行接口、USB接口、扩展槽（Slots） 、直流电源插座、可充电电池以及各种条线。图中从上到下，左到右：内存条，磁盘、光驱等的数
23、据线接口；CPU 风扇（一般下面是散热器，和 CPU） ；棕色 AGP 槽：只能接显卡；白色 PCI 槽：能接显卡、网卡、声卡等。图 2-2 CPU = 运算器+控制器图 2-3 Alan Turing, founder of computer science, and artificial intelligencehttp:/ 图灵是举世罕见的天才数学家和计算机科学家，仅仅在世 42 年。他的英年早逝,像他横溢的才华一样，令世界吃惊与难以置信。生命虽然短暂，但那传奇第 2 章 计算机系统 13 的人生，丰富多彩的创造力和智慧而深邃的思想，使他犹如一颗耀眼的明星，持续地照耀着人间后世在科学的浩
24、瀚太空里探索未来的人们。 自上个世纪 60 年代以来,计算机技术飞速发展,信息产业逐渐成为影响人类社会的最重要的工业之一。支持技术与工业发展的理论基础是计算机科学。众所周知， “诺贝尔奖”是世界上最负盛名的奖项,但仅用于奖励那些在物理、化学、文学、医学、经济学与促进世界和平等方面做出开拓性重大贡献的人士。“图灵奖”则是计算机科学领域的最高奖项,有“计算机界诺贝尔奖”之称。设立这个大奖，既是为了促进计算机科学的进一步发展，也是为了纪念一位天才数学家、计算机科学的奠基人艾兰图灵。http:/zh.wikipedia.org/wiki/图灵 图灵被视为计算机科学之父。1931 年进入剑桥大学国王学院
25、，毕业后到美国普林斯顿大学攻读博士学位，二战爆发后回到剑桥，后曾协助军方破解德国的著名密码系统 Enigma，帮助盟军取得了二战的胜利。图灵对于人工智能的发展有诸多贡献，例如图灵曾写过一篇名为机器会思考吗？ （Can Machine Think?）的论文，其中提出了一种用于判定机器是否具有智能的试验方法，即图灵试验。至今，每年都有试验的比赛。此外，图灵提出的著名的图灵机模型为现代计算机的逻辑工作方式奠定了基础。http:/ short video describing the life and unfortunate death of Alan Turing.http:/zh.wikipedi
26、a.org/wiki/姚期智姚期智，美籍华人，计算机科学家，2000 年图灵奖得主，是目前唯一一位获得此奖项的华人及亚洲人。目前是清华大学理论计算机科学研究中心教授。 因为对计算理论，包括伪随机数生成，密码学与通信复杂度的诸多贡献，美国计算机协会（ACM ）决定把该年度的图灵奖授予他。 Data processorsFigure 1.1 A signle purpose computing machine第 2 章 计算机系统 14 Before discussing the Turing model, let us define a computer as a data processor.
27、 Using this definition, a computer acts a black box that accepts input data, processes the data, and created output data (Figure 1.1). Although this model can define the functionality of a computer today, it is too general. In this model, a pocket calculator is also a computer (which it is, in a lit
28、eral sense).Another problem with this model is that it does not specify the type of processing, or whether more than one type of processing is possible. In other words, it is not clear how many types or sets of operations a machine based on this model can perform. Is it a specific-purpose machine or
29、 a general-purpose machine?This model could represent a specific-purpose computer (or processor) that is designed to do a single job, such as controlling the temperature of a building or controlling the fuel usages in a car. However, computers, as the term is used today, are general-purpose mahines.
30、 They can do many different types of tasks. This implies that we need to change this model into the Turing model to be able to reflect the actual computers of today.Programmable data processorsThe Turing model is a better model for a general-purpose computer. This model adds an extra element to the
31、specific computing machine: the program. A program is a set of instructions that tells the computer what to do with data. Figure 1.2 shows the Turing model.In the Turing model, the output data depends on the combination of two factors: the input data and the program. With the same input, we can gene
32、rate different outputs if we change the program. Similarly, with the same program, we can generate different outputs if we change the input data. Finally, if the input data and the program remain the same, the output should be the same. Let us look at three cases.Figure 1.2 A computer based on the T
33、uring model: programmable data processorFigure 1.3 shows the same sorting program with different input data, although the program is the same, the outputs are different, because different input data is 第 2 章 计算机系统 15 processed.Figure 1.3 The same program, different dataFigure 1.4 shows the same inpu
34、t data with different programs. Each program makes the computer perform different operations on the input data. The first program sorts the data, the second adds the data, and the thired finds the smallest number.Figure 1.4 The same input, different programWe expect the same result each time if both
35、 input data and the program are the same, of course. In other words, when the same program is run with the same input data, we expect the same output.第 2 章 计算机系统 16 The universal Turing machineA universal Turing machine, a machine that can do any computation if the appropriate program is provided, w
36、as the first description of a modern computer. It can be proved that a very powerful computer and a universal Turing machine can compute the same thing. We need only provide the data and the program - the description of how to do the computation - to either machine. In fact, a universal Turing machi
37、ne is capable of computing anything that is computable.A computer is a machine that manipulates data according to a list of instructions.2.1.2 VON NEUMANN MODELComputers built on the Turing universal machine store data in their memory. Around 1944-1945, John von Neumann proposed that, since program
38、and data are logically the same, programs should also be stored in the memory of a computer.Four subsystemsComputers built on the von Neumann model divide the computer hardware into four subsystems: memory, arithmetic logic unit, control unit, and input/output (Figure 1.5).Figure 1.5 von Neumann mod
39、elMemory is the storage area. This is where programs and data are stored during 第 2 章 计算机系统 17 processing. We discuss the reasons for storing programs and data later in the chapter.The arithmetic logic unit (ALU) is where calculation and logical operations take place. For a computer to act as a data
40、 processor, it must be able to do arithmetic operations on data (such as adding a list of numbers). It should also be able to do logical operations on data.The control unit controls the operations of the memory, ALU, and the input/output subsystmes.The input subsystem accepts input data and the prog
41、ram from outside the computer, while the output subsystem sends results of processing to the outside world. The definition of the input/output subsystem is very broad: it also includes secondary storage devices such as disk or tape that store data and programs for processing. When a disk stores data
42、 that results from processing, it is considered an output device; when data is read from the disk, it is considered as a input device.The stored program conceptThe von Neumann model states that the program must be stored in memory. This is totally different from the arthiteccure of early computers i
43、n which only the data was stored in memory; the programs for their tasks implemented by manipulating a set of switches or by changing the wiring system.The memory of modern computers hosts both a program and its corresponding data. This implies that both the data and programs should have the same fo
44、rmat, because they are stored in memory. In fact, they are stored as binary patterns in memory - a sequence of 0s and 1s.Sequential execution of instructionsA program in the von Neumann model is made of a finite number of instructions. In this model, the control unit fetches one instruction from mem
45、ory, decodes it, and then executes it. In other words, the instructions are executed one after another. Of course, one instruction may request the control unit to jump to some previous or following instructions, but this does not mean that the instructions are not executed sequentially. Sequential e
46、xecution of a program was the initial requirement of a computer based on the von Neumann model. Todays computers execute programs in the order that is most efficient.第 2 章 计算机系统 18 2.1.3 Computer componentsWe can think of a computer as being made up of three components: computer hardware, data, and
47、computer software.Computer hardwareComputer hardware today has four components under the von Neumann model, although we can have different types of memory, different types of input/output subsystems, and so on.DataThe von Neumann model clearly defines a computer as a data processing machine that acc
48、epts the input data, processes it, and outputs the result.The von Neumann model does not define how data must be stored in a computer. If a computer is an electronic device, the best way to store data is in the form of an electrical signal, specifically its presence or absence. This implies that a computer can store data in one of two states.Obviously, the data we use in daily life is
