Chapter 1 The Big Picture

2 25 Chapter Goals Describe the layers of a computer system Describe the concept of abstraction and its relationship to computing Describe the history of computer hardware and software Describe the changing role of the computer user Distinguish between systems programmers and applications programmers Distinguish between computing as a tool and computing as a discipline

3 2 Computing systems are dynamic and highly interactive! What is the difference between hardware and software? Computing Systems

4 3 Hardware The physical elements of a computing system (printer, circuit boards, wires, keyboard…) Software The programs that provide the instructions for a computer to execute Computing Systems

5 4 Layers of a Computing System

6 5 Abstraction A mental model that removes complex details This is a key concept. Abstraction will reappear throughout the text – be sure you understand it! Abstraction

7 Internal View

8 Abstract View

9 History

10 6 Abacus An early device to record numeric values Blaise Pascal Mechanical device to add, subtract, divide & multiply Joseph Jacquard Jacquard’s Loom, the punched card Charles Babbage Analytical Engine Early History of Computing

11 7 Ada Lovelace First Programmer, the loop Alan Turing Turing Machine, Artificial Intelligence Testing Early History of Computing

12 The First Computers Harvard Mark I, ENIAC, UNIVAC I Early computers launch new era in mathematics, physics, engineering and economics “Where a calculator on the ENIAC is equipped with 18,000 vacuum tubes and weighs 30 tons, computers in the future may have only 1,000 vacuum tubes and perhaps weigh 1.5 tons.” (Popular Mechanics, 1949)

13 8 Vacuum Tubes Large, not very reliable, generated a lot of heat Magnetic Drum Memory device that rotated under a read/write head Card Readers  Magnetic Tape Drives Sequential auxiliary storage devices First Generation Hardware ( )

14 9 Transistor Replaced vacuum tube, fast, small, durable, cheap Magnetic Cores Replaced magnetic drums, information available instantly Magnetic Disks Replaced magnetic tape, data can be accessed directly Second Generation Hardware ( )

15 10 Integrated Circuits Replaced circuit boards, smaller, cheaper, faster, more reliable Transistors Now used for memory construction Terminal An input/output device with a keyboard and screen Third Generation Hardware ( )

16 11 Large-scale Integration Great advances in chip technology PCs, the Commercial Market, Workstations Personal Computers and Workstations emerge New companies emerge: Apple, Sun, Dell … Laptops Everyone has his/her own portable computer Fourth Generation Hardware (1971- ?)

17 12 Parallel Computing Computers rely on interconnected central processing and/or memory units that increase processing speed “ Real concurrency -- in which one program actually continues to function while you call up and use another -- is more amazing but of small use to the average person. How many programs do you have that take more than a few seconds to perform any task?” New York Times, 1989 Parallel Computing

18 12 Networking Ethernet connects small computers to share resources File servers connect PCs in the late 1980s ARPANET and LANs  Internet “Transmission of documents via telephone wires is possible in principle, but the apparatus required is so expensive that it will never become a practical proposition.” Dennis Gabor, 1962 Networking

19 13 Machine Language Computer programs written in binary (1s and 0s) Assembly Languages and Translators Programs written using mnemonics, which were translated into machine language Programmer Changes Programmers divide into two groups: application programmers and systems programmers First Generation Software ( )

20 Assembly/Machine Systems programmers write the assembler (translator) Applications programmers use assembly language to solve problems

21 14 High-level Languages English-like statements made programming easier: Fortran, COBOL, Lisp Second Generation Software ( ) Systems programmers write translators for high-level languages Application programmers use high-level languages to solve problems

22 15 Third Generation Software ( ) Systems Software Utility programs Language translators Operating system, which decides which programs to run and when Separation between Users and Hardware Computer programmers write programs to be used by general public (i.e., nonprogrammers)

23 16 Third Generation Software ( )

24 17 Structured Programming Pascal C++ New Application Software for Users Spreadsheets Word processors Database management systems Fourth Generation Software ( )

25 18 Microsoft Windows operating system and other Microsoft application programs dominate the market Object-Oriented Design Based on a hierarchy of data objects (i.e. Java) World Wide Web Allows easy global communication through the Internet New Users Today’s user needs no computer knowledge Fifth Generation Software (1990- present)

26 20 Programmer / User Applications Programmer (uses tools) User with No Computer Background Systems Programmer (builds tools) Domain-Specific Programs Computing as a Tool

27 21 Computing as a Discipline What can be (efficiently) automated? Four Necessary Skills Algorithmic Thinking Representation Programming Design

28 Is Computer Science a mathematical, scientific, or engineering discipline? 22 What do you think? Computing as a Discipline

29 23 Examples of Systems Areas Algorithms and Data Structures Programming Languages Architecture Operating Systems Software Engineering Human-Computer Communication

30 24 Examples of Application Areas Numerical and Symbolic Computation Databases and Information Retrieval Intelligent Systems Graphics and Visual Computing Net-Centric Computing Computational Science

31 Ethical Issues The Digital Divide What is it? How does it affect you? What is computer literacy for your sister, the musician? your brother, the doctor? your sister, the kindergarten teacher? Is it important to try to bridge the digital divide?

32 Who am I? Can you list three items on my resume?

33 Do you know? What computer company was launched in a garage? What branch of mathematics is being used in terrorist detection? What is Room to Read? When and where were the first CS Departments formed?