Class 1: Class 1: What is Introduction Introduction Computer - PDF document

Class 1: Class 1: What is Introduction Introduction Computer Science ? CS1120 Fall 2010 University of Virginia Computer Science Westley Weimer http://www.cs.virginia.edu/cs1120 #2 The note on the inflected line is Let AB and CD be the two given numbers only difficult to you, because it is so not relatively prime. It is required to find easy. There is in fact nothing in it, the greatest common measure of AB and but you think there must be some CD . grand mystery hidden under that word inflected ! If now CD measures AB , since it also Whenever from any point measures itself, then CD is a common without a given line, you draw along measure of CD and AB . And it is manifest to any point in the given line, you that it is also the greatest, for no greater have inflected a line upon a given number than CD measures CD . line. Ada Byron (age 19), letter to Annabella Euclid’s Elements, Book VII, Proposition 2 (300BC) Acheson (explaining Euclid), 1834 #3 #4 I ask you: By the word operation, we mean any process which alters the mutual relation of two or What's the more things, be this relation of what kind it difference may. This is the most general definition, and would include all subjects in the universe... between Euclid Supposing, for instance, that the fundamental and Ada? relations of pitched sounds in the science of harmony and of musical composition were I have no idea what susceptible of such expression and you're talking about adaptations, the engine might compose when you say the word elaborate and scientific pieces of music of any degree of complexity or extent. “ask”. Bill Gates (deposition at Ada Byron, 1843 Microsoft’s anti-trust trial) #5 #6

Today's Class Geometry vs. Computer Science • Ada and Euclid • Geometry (mathematics) is about declarative knowledge: “what is” • Engineering and Science If now CD measures AB , since it also measures itself, • Moore's Law and Computing Power then CD is a common measure of CD and AB • The Liberal Arts • Computer Science is about imperative • Course Expectations knowledge: “how to” • Recursive Definitions and Languages • Nuclear Weapons • Formal Languages and Systems #7 #8 Computer Science Geometry vs. Computer Science “How to” knowledge: • Geometry (mathematics) is about declarative knowledge: “what is” • Ways of describing information processes (computations) If now CD measures AB , since it also measures itself, Language then CD is a common measure of CD and AB • Computer Science is about imperative • Ways of predicting properties of knowledge: “how to” information processes Logic Computer Science has little to do with beige (or spiffy black) boxes called “computers” and is not a real science. #9 #10 Science? Science, Engineering or Other? • Science involves 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 is not a real science #11 #12

Engineering? Liberal Arts Trivia: Music “ Engineering is design under • Q. What is the name of a musical scale with constraint … Engineering is synthetic twelve pitches, each a semitone or half step - it strives to create what can be, apart? Such a scale is nondiatonic, consisting but it is constrained by nature, by entirely of half-step intervals and having no cost, by concerns of safety, tonic due to the symmetry or equal spacing of reliability, environmental impact, its tone. manufacturability, maintainability and many other such 'ilities.' ...” William Wulf and George Fisher, 2002 #13 #14 Liberal Arts Trivia: Psychology Let's Start With Classic Computers • Say the color each word is printed in: • Green Red Blue • Purple Blue Purple • Blue Purple Red • Green Purple Green • Q. Name the effect that refers to the fact that naming the color of the first group of words is easier and quicker than the second. #15 #16 Apollo Guidance Computer, 1969 Measuring 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 choices Why did they need to fit the 1 Cubic Foot guidance computer in the rocket? #17 #18

Computing Power 1969-present How much power? (in Apollo Control Computer Units) • Apollo Computer: 61440 bits of changeable memory 80,000,000 • Lab machines have 1 GB (RAM) Moore’s “Law”: computing power 70,000,000 – 1 Gigabyte = 1024 Megabytes, roughly doubles every 18 months! 1 Megabyte = 1024 Kilobytes, 60,000,000 You will understand this 1 Kilobyte = 1024 Bytes, 50,000,000 notation soon…but don’t worry if you don’t now 1 Byte = 8 bits 40,000,000 > (* 1024 1024 1024 8) 30,000,000 ~ 8.6 Billion bits 8589934592 20,000,000 > (round (/ (* 1024 1024 1024 8) 61440)) 10,000,000 139810 You have 139 810 times more power than AGC 0 1969 1972 1975 1978 1981 1984 1987 1990 1993 1996 1999 2002 2005 2008 If Apollo Guidance Computer power is 1 inch, you have 2.2 miles! #19 So, what is computer science? Constraints Computer Scientists Face • Not like those for engineers: • Science – Cost, weight, physics, etc. – No: it's about fake things like numbers, not about observing and understanding nature – If today's ~20 Million times what people had in 1969 isn’t enough for you, wait until 2011 • Engineering and you will have ~80 Million times… – No: we don’t have to deal with engineering- • More like those for Musicians and Poets: type constraints – Imagination and Creativity • Liberal Art – Complexity of what we can understand #21 #22 Liberal Arts: ~1100 AD The Liberal Arts language • Illiberal Arts numbers – arts for the non-free: pursued for economic reasons Quadrivium (4 roads) Trivium (3 roads) • Liberal Arts – arts for the free : pursued for intrinsic reasons Arithmetic Grammar Logic Music Rhetoric study of meaning in argument numbers written expression Comprehension Geometry for in time of discourse discovering quantification Astronomy truth of space We will see all of these in this class! #23 #24