Slide 1What is Computer Science?Slide 3Slide 4Slide 5What is the difference between Euclid and Ada?Geometry vs. Computer ScienceComputer ScienceScience, Engineering, Other?Science?Engineering?Apollo Guidance Computer, 1969Measuring ComputersHow much power?Computing Power 1969-2005 (in Apollo Control Computer Units)Constraints Computer Scientists FaceSo, what is computer science?Liberal Arts: ~1100The Liberal ArtsCourse ExpectationsCourse RoadmapWhat You Should ExpectLike Drinking from a FirehoseHelp AvailableWhat I Expect of YouBackground ExpectedA Course for Everyone!Shameless PitchFirst Main Theme: Recursive DefinitionsSlide 30According to GuinnessMaking Longer WordsLanguage is RecursiveRecursive DefinitionsSlide 35ChargeThanks!1CS150 Fall 2005: 1. IntroductionDavid Evanshttp://www.cs.virginia.edu/evansCS150: Computer ScienceUniversity of VirginiaComputer ScienceClass 1: Class 1: IntroductionIntroduction2CS150 Fall 2005: 1. IntroductionWhat is Computer Science?3CS150 Fall 2005: 1. IntroductionLet AB and CD be the two given numbers not relatively prime. It is required to find the greatest common measure of AB and CD.If now CD measures AB, since it also measures itself, then CD is a common measure of CD and AB. And it is manifest that it is also the greatest, for no greater number than CD measures CD. Euclid’s Elements, Book VII, Proposition 2 (300BC)4CS150 Fall 2005: 1. IntroductionThe note on the inflected line is only difficult to you, because it is so easy. There is in fact nothing in it, but you think there must be some grand mystery hidden under that word inflected! Whenever from any point without a given line, you draw a long to any point in the given line, you have inflected a line upon a given line.Ada Byron (age 19), letter to Annabella Acheson (explaining Euclid), 18345CS150 Fall 2005: 1. IntroductionBy the word operation, we mean any process which alters the mutual relation of two or more things, be this relation of what kind it may. This is the most general definition, and would include all subjects in the universe... Supposing, for instance, that the fundamental relations of pitched sounds in the science of harmony and of musical composition were susceptible of such expression and adaptations, the engine might compose elaborate and scientific pieces of music of any degree of complexity or extent.Ada Byron, 18436CS150 Fall 2005: 1. IntroductionWhat is the difference between Euclid and Ada?“It depends on what your definition of ‘is’ is.” Bill Gates (at Microsoft’santi-trust trial)7CS150 Fall 2005: 1. IntroductionGeometry vs. Computer Science•Geometry (mathematics) is about declarative knowledge: “what is” If now CD measures AB, since it also measures itself, then CD is a common measure of CD and AB•Computer Science is about imperative knowledge: “how to”Computer Science has little to do with beige (or translucent blue) boxes called “computers” and is not a real science.8CS150 Fall 2005: 1. IntroductionComputer Science“How to” knowledge:•Ways of describing information processes (computations)•Ways of predicting properties of information processes LanguageLogicWhat kinds of things do we want to predict?9CS150 Fall 2005: 1. IntroductionScience, Engineering, Other?10CS150 Fall 2005: 1. IntroductionScience?•Understanding Nature through Observation–About real things like bowling balls, black holes, antimatter, electrons, comets, etc.•Math and Computer Science are about fake things like numbers, graphs, functions, lists, etc.–Computer Science is a useful tool for doing real science, but not a real science11CS150 Fall 2005: 1. IntroductionEngineering?“Engineering is design under constraint… Engineering is synthetic - it strives to create what can be, but it is constrained by nature, by cost, by concerns of safety, reliability, environmental impact, manufacturability, maintainability and many other such 'ilities.' ...” William Wulf12CS150 Fall 2005: 1. IntroductionApollo Guidance Computer, 19691 Cubic FootWhy did they need to fit the guidance computer in the rocket?13CS150 Fall 2005: 1. IntroductionMeasuring Computers•1 bit = smallest unit of information–True or False–0 or 1–If we start with 2 possible choices, and get 1 bit, we can eliminate one of the choices14CS150 Fall 2005: 1. IntroductionHow much power?•Apollo Computer: 30720 bits of changeable memory •Lab machines have 512 MB (RAM)–1 Megabyte = 1024 Kilobytes, 1 Kilobyte = 1024 Bytes, 1 Byte = 8 bits–512 MB > (* 512 1024 1024 8) 4294967296 ~ 4.3 Billion bits > (round (/ (* 386 1024 1024 8) 30720))139810If Apollo Guidance Computer power is 1 inch, you have 2.2 miles!You have 105 404 times more power than AGCYou will understand thisnotation soon…but don’t worryif you don’t now15CS150 Fall 2005: 1. IntroductionComputing Power 1969-2005(in Apollo Control Computer Units)Moore’s Law: computing power doubles every 18 months!16CS150 Fall 2005: 1. IntroductionConstraints Computer Scientists Face•Not like those for engineers:–Cost, weight, physics, etc.–If ~8 Million times what people had in 1969 isn’t enough for you, wait until 2007 and you will have 20 Million times…•More like those for Musicians and Poets:–Imagination and Creativity–Complexity of what we can understand17CS150 Fall 2005: 1. IntroductionSo, what is computer science?•Science–No: its about fake things like numbers, not about observing and understanding nature •Engineering–No: we don’t have to deal with engineering-type constraints•Liberal Art18CS150 Fall 2005: 1. IntroductionLiberal Arts: ~1100•Illiberal Arts–arts for the non-free: pursued for economic reasons•Liberal Arts–arts for the free: pursued for intrinsic reasons19CS150 Fall 2005: 1. IntroductionThe Liberal ArtsTrivium (3 roads)languageQuadrivium (4 roads)numbersGrammarstudy of meaning in written expressionRhetoriccomprehension of discourseLogicargument for discovering truthArithmeticGeometryquantification of spaceMusicnumber in timeAstronomyWe will see all of these in this class!20CS150 Fall 2005: 1. IntroductionCourse Expectations21CS150 Fall 2005: 1. IntroductionCourse RoadmapComputer Science from Euclid and Ada to Quantum Computing and the World Wide Web1st ClassPS 6-7Lecture PS 1-5Liberal Arts(Intellectual)Illiberal Arts($$$$)22CS150 Fall 2005: 1. IntroductionWhat You Should Expect•The fourth (?) coolest class at UVa–Less cool than PHYE162, PHYE163, PHYE164•This course will be