CMSC 330: Organization of Programming Languages A Brief History of Programming Languages CMSC 330 2 Babylon • Founded roughly 4000 years ago – Located near the Euphrates River, 56 mi south of Baghdad, Iraq • Historically influential in ancient western world • Cuneiform writing system, written on clay tablets – Some of those tablets survive to this day – Those from Hammurabi dynasty (1800-1600 BC) include mathematical calculations • (Also known for Code of Hammurabi, an early legal code) CMSC 330 3 A Babylonian Algorithm A [rectangular] cistern. The height is 3, 20, and a volume of 27, 46, 40 has been excavated. The length exceeds the width by 50. You should take the reciprocal of the height, 3, 20, obtaining 18. Multiply this by the volume, 27, 46, 40, obtaining 8, 20. Take half of 50 and square it, obtaining 10, 25. Add 8, 20, and you get 8, 30, 25 The square root is 2, 55. Make two copies of this, adding [25] to the one and subtracting from the other. You find that 3, 20 [i.e., 3 1/3] is the length and 2, 30 [i.e., 2 1/2] is the width. This is the procedure. – Donald E. Knuth, Ancient Babylonian Algorithms, CACM July 1972 The number n, m represents n*(60k) + m*(60k-1) for some k CMSC 330 4 More about Algorithms • Euclid’s Algorithm (Alexandria, Egypt, 300 BC) – Appeared in Elements – Computes gcd of two integers let rec gcd a b = if b = 0 then a else gcd b (a mod b) • Al-Khwarizmi (Baghdad, Iraq, 780-850 AD) – Al-Khwarizmi Concerning the Hindu Art of Reckoning – Translated into Latin (in 12th century?) • Author’s name rendered in Latin as algoritmi • Thus the word algorithmCharles Babbage (1791–1871) • British mathematician & mechanical engineer • Invented concept of a programmable computer – Partially built a Difference Engine CMSC 330 5 ! A mechanical calculator for computing polynomials ! Uses finite difference method to avoid multiplication & division ! Never completely finished ! Model built in 1991 at the London Science Museum CMSC 330 6 The Analytical Engine (1837) • Babbage described plans for an Analytical Engine – Digital, programmable using punch cards – Included branching, looping, arithmetic, and storage – Memory would store 1000 numbers w/ 500 digits each – Language similar to assembly language – Powered by steam engine • Partially constructed by 1910 – Used to compute a list of multiples of ! • If built, would have been 1st Turing-complete computation device CMSC 330 7 Ada Lovelace (1815-52) • British mathematician – Corresponded with Babbage from 1833 on – In 1843, translated Italian mathematician L. Menabrea's memoir on Babbage’s proposed Analytical Engine – Appended notes on how to program the Analytical Engine to calculate Bernoulli numbers – Recognized by historians as 1st published program – Making her world’s 1st programmer • Ada programming language (1983) – Imperative, object-oriented language based on Pascal – Named in her honor CMSC 330 8 Alonzo Church (1903-1995) • Mathematician at Princeton Univ. • Three key contributions: – The lambda calculus (lectures in 1936, publ. 1941) – Church’s Thesis • All effective computation is expressed by recursive (decidable) functions – Church’s Theorem • First order logic is undecidableCMSC 330 9 Alan Turing (1912 - 1954) • The father of modern computer science – Dissertation work advised by Church at Princeton – Formulated the Turing machine (~1936) (A more general form of abstract computer. We’ve already looked at simpler versions like DFA and PDA) • ! – A finite alphabet • Q – a set of states • s Q – A start state • F ⊆ Q – The final states • " : Q # ! $ Q # ! # {L, R} – If "(q, a) = (q', a', d), then if we’re in state q and see a on the tape, then replace it by a', move to state q', and move the position of the tape either left or right – A formal definition of a computable algorithm CMSC 330 10 Other Early Computers • ABC (1939-1942) – Atanasoff and Berry Computer, at Iowa State Univ. – First electronic digital computer • As decided by a judge in 1973! (Invalidated ENIAC patent) • Z3 (1945) – Konrad Zuse, essentially isolated from everyone else – Used Plankalkül, a sophisticated programming lang. • But no one knew about his results, so not influential CMSC 330 11 Other Early Computers (cont’d) • Harvard Mark I (1944) – Aiken, IBM – Electronic, used relays • ENIAC (1946) – Electronic Numerical Integrator and Computer – Developed by Eckert and Mauchly at UPenn – Electronic, general purposes – Used vacuum tubes – For 30 years considered the “first” electronic computer • Until court case gave honor to ABC • Supposedly Eckert and Mauchley overheard Atanasoff discussing designs for ABC CMSC 330 12 The First Programming Languages • Early computers could be “programmed” by rewiring them for specific applications – Tedious, error prone • John von Neumann (1903-1957) – Three CS contributions (famous for lots of other stuff) • von Neumann machine – the way computers are built today – A stored program architecture » Program stored in memory as data, so can be modified – (Unclear that he actually invented this...) • “Conditional control transfer” – if and for statements – Allows for reusable code, like subroutines • Merge sort algorithmCMSC 330 13 Pseudocodes (Assembly Interpreter) • Short Code (1949) – John Mauchly – Interpreted instructions • E.g., X0 = sqrt(abs(Y0)) becomes 00 X0 03 20 06 Y0 – 06 = abs, 20 = sqrt, 03 = assignment – But needed to translate by hand • A-0 Compiler (1951; Grace Murray Hopper) – Translated symbolic code into machine code • Sounds like an assembler... – Assigned numbers to routines stored on tape • Which would then be retrieved and put in memory Eckert and Mauchly CMSC 330 14 FORTRAN (1954 - 1957) • FORmula TRANslator • Developed at IBM by John Backus et al – Aimed at scientific computation – Computers slow, small, unreliable • So FORTRAN needed to produce efficient code • Features (FORTRAN I) – Variable names
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