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Algorithm 1: The Morning Routine Get out of bed Shower Bathe kids Prepare cereal. Algorithm 1: The Morning Routine Get out of bed Shower Bathe kids Prepare.

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Presentation on theme: "Algorithm 1: The Morning Routine Get out of bed Shower Bathe kids Prepare cereal. Algorithm 1: The Morning Routine Get out of bed Shower Bathe kids Prepare."— Presentation transcript:

1 Algorithm 1: The Morning Routine Get out of bed Shower Bathe kids Prepare cereal. Algorithm 1: The Morning Routine Get out of bed Shower Bathe kids Prepare cereal. Math 130 Intro to Computer Programming Algorithms Lecture # 01 01/21/05 Math 130 Intro to Computer Programming Algorithms Lecture # 01 01/21/05 B Smith: Required 45 to 50 minutes. Stirred up few questions. Needs to be more interactive and less general/abastract. Score 3 with improv, 2.5 if used as is. B Smith: Required 45 to 50 minutes. Stirred up few questions. Needs to be more interactive and less general/abastract. Score 3 with improv, 2.5 if used as is. B Smith: Great for independent study; not so great otherwise. B Smith: Great for independent study; not so great otherwise. B Smith: Not used Fall05. Not needed; not helpful B Smith: Not used Fall05. Not needed; not helpful

2 2 Overview Solving problems –mysterious or methodical –luck or by design Algorithms –recipes Values and variables –quantity and place holders

3 3 How do we solve problems? Largely empirical –“Doing heart surgery in this manner works” History –“This is how Alice did it…” Inspiration –“I don’t know how, but I solved it!” Brute force –Trial-and-error The scientific method

4 … sterilize(saw,alcohol); raise_hammer(); lower_hammer(fast); start(saw); /* etc. etc. */ Patient has elevated pressure in anterior parietal lobe The Problem-solving Process Problem specification Algorithm Program Executable ( solution ) Design Implementation Compilation "Doctor, my head hurts" Analysis 1. Sterilize cranial saw 2. Anaesthetize patient 3. Remove top of skull 4. Get the big spoon etc., etc. B Smith: Use math as a useful application. How about finding the roots of 2x^2+3x-4 = 0? What would be the algorithm. B Smith: Use math as a useful application. How about finding the roots of 2x^2+3x-4 = 0? What would be the algorithm.

5 5 The Problem-solving Process Problem specification Algorithm Program Executable (solution) Analysis Design Implementation Compilation

6 6 A sequence of instructions specifying the steps required to accomplish some task Named after: –Muhammad ibn Mūsā al-Khwārizmi –Circa C.E. (Common Era) Algorithm

7 7 Algorithm –History Muhammad ibn Musa al-Khwarizmi Book on arithmetic: –Hindu numeration, decimal numbers, use of zero, method for finding square root –Latin translation (c.1120 CE): “Algoritmi de numero Indorum” Book on algebra – “Kitāb al-jabr wa’l-muqābala” (“Rules of restoring and equating”)

8 8 A sequence of instructions describing how to do a task Algorithm – Working Definition As opposed to actually executing the instructions!

9 9 sterilize(saw,alcohol); raise_hammer(); lower_hammer(fast); start(saw); /* etc. etc. */ The Problem-solving Process Problem specification Algorithm Program Executable (solution) Analysis Design Implementation Compilation " Doctor, my head hurts" Patient has elevated pressure in anterior parietal lobe. 1. Sterilize cranial saw 2. Anaesthetize patient 3. Remove top of skull 4. Get the big spoon etc., etc

10 10 Algorithm -- Examples A cooking recipe Assembly instructions for a model car, boat, etc. The rules of how to play a game VCR instructions Description of a martial arts technique Directions for driving from A to B A knitting pattern A car repair manual

11 11 Algorithm – Examples (cont) Recipe for Almond and honey slice Recipe for Arroz con pollo

12 12 Almond and Honey Slice 1/2 quantity Shortcrust Pastry 185 g unsalted butter 100 g castor sugar 5 tablespoons honey 50 ml cream 50 ml brandy or any other liqueur or spirit 300 g flaked almonds Preheat oven for 200° C Line a 30 cm  20 cm baking tray with baking paper, and then with pastry Bake blind for 20 minutes, then remove weights and foil Turn oven up to 220° C. Bring remaining ingredients to a boil, stirring. Spread evenly over pastry. Bake until topping is bubbling and has caramelized evenly, about 15 minutes. Cool before cutting into fingers or squares. From: Stephanie Alexander, The Cook’s Companion, Viking/Penguin, Ringwood, Victoria, 1996, p. 349.

13 13 Almond and Honey Slice 1/2 quantity Shortcrust Pastry 185 g unsalted butter 100 g castor sugar 5 tablespoons honey 50 ml cream 50 ml brandy or any other liqueur or spirit 300 g flaked almonds Preheat oven for 200° C Line a 30 cm  20 cm baking tray with baking paper, and then with pastry Bake blind for 20 minutes, then remove weights and foil Turn oven up to 220° C. Bring remaining ingredients to a boil, stirring. Spread evenly over pastry. Bake until topping is bubbling and has caramelized evenly, about 15 minutes. Cool before cutting into fingers or squares. From: Stephanie Alexander, The Cook’s Companion, Viking/Penguin, Ringwood, Victoria, 1996, p Instructions are given in the order in which they are performed (“executed”)

14 14 Correct Algorithm? Cut chicken into pieces and brown the pieces on all sides in a casserole dish in hot olive oil. Remove the chicken; to the juices in the casserole add garlic, onions and green peppers, and sauté until onion is golden. Add bay leaf, whole tomatoes, and chicken broth. When the broth boils add salt, saffron and rice. Arrange chicken on rice, cover casserole and bake in a moderate oven (350°F) for 20 minutes or until the rice is tender. Add beans and artichokes during last 10 minutes of cooking. From: “Arroz Con Pollo” in The Margaret Fulton Cookbook, Hamlyn, Sydney, 1968.

15 15 Cut chicken into pieces and brown the pieces on all sides in a casserole dish in hot olive oil. Remove the chicken and to the juices in the casserole add garlic, onions and green peppers, and sauté until onion is golden. Add bay leaf, whole tomatoes, and chicken broth. When the broth boils add salt, saffron and rice. Arrange chicken on rice, cover casserole and bake in a moderate oven (350°F) for 20 minutes or until the rice is tender. Add beans and artichokes during last 10 minutes of cooking. From: “Arroz Con Pollo” in The Margaret Fulton Cookbook, Hamlyn, Sydney, Correct Algorithm?

16 16 Cut chicken into pieces and brown the pieces on all sides in a casserole dish in hot olive oil. Remove the chicken and to the juices in the casserole add garlic, onions and green peppers, and sauté until onion is golden. Add bay leaf, whole tomatoes, and chicken broth. When the broth boils add salt, saffron and rice. Arrange chicken on rice, cover casserole and bake in a moderate oven (350°F) for 10 minutes. Add beans and artichokes. Cover, and bake for another 10 minutes or until rice is tender. Correct Algorithm?

17 17 From Algorithms to Programs Problem C Program Algorithm Algorithm: A sequence of instructions describing how to do a task (or process)

18 18 Components of an Algorithm Variables and values Instructions Sequences Procedures Selections Repetitions Documentation

19 19 Values Represent quantities, amounts, rates, etc. May be numerical, alphabetical or even other items A related unit may or may not be specified –Add 3 cups of flour –Pull rip-cord Example: –Recipe ingredients (how big, how hot, how long)

20 20 Almond and Honey Slice 1/2 quantity Shortcrust Pastry 185 g unsalted butter 100 g castor sugar 5 tablespoons honey 50 ml cream 50 ml brandy or any other liqueur or spirit 300 g flaked almonds Preheat oven for 200° C Line a 30 cm  20 cm baking tray with baking paper, and then with pastry Bake blind for 20 minutes, then remove weights and foil Turn oven up to 220° C. Bring remaining ingredients to a boil, stirring. Spread evenly over pastry. Bake until topping is bubbling and has caramelised evenly, about 15 minutes. Cool before cutting into fingers or squares. From: Stephanie Alexander, The Cook’s Companion, Viking/Penguin, Ringwood, Victoria, 1996, p. 349.

21 21 Almond and Honey Slice 1/2 quantity Shotcrust Pastry 185 g unsalted butter 100 g castor sugar 5 tablespoons honey 50 ml cream 50 ml brandy or any other liqueur or spirit 300 g flaked almonds Preheat oven for 200° C Line a 30 cm  20 cm baking tray with baking paper, and then with pastry Bake blind for 20 minutes, then remove weights and foil Turn oven up to 220° C. Bring remaining ingredients to a boil, stirring. Spread evenly over pastry. Bake until topping is bubbling and has caramelised evenly, about 15 minutes. Cool before cutting into fingers or squares. From: Stephanie Alexander, The Cook’s Companion, Viking/Penguin, Ringwood, Victoria, 1996, p. 349.

22 22 Variables This jar can contain 10 cookies 50 grams of sugar 3 slices of cake etc. ValuesVariable Are containers for values – places to store values Example:

23 23 Restrictions on Variables Variables may be restricted to contain a specific type of value

24 24 Components of an Algorithm Values and Variables Instruction (a.k.a. primitive) Sequence (of instructions) Procedure (involving instructions) Selection (between instructions) Repetition (of instructions) Documentation (beside instructions)

25 25 Instructions (Primitives) Some action that is simple......and unambiguous......that the system knows about......and should be able to actually do

26 26 Instructions – Examples Take off your shoes Count to 10 Cut along dotted line Knit 1 Purl 2 Firmly Pull rip-cord Sift 10 grams of sulfur Directions to perform specific actions on values and variables.

27 27 Instructions -- Application Some instructions can only be applied to specific types of values or variables Examples:

28 28 Instructions (Primitives) -- Recommendations When writing an algorithm, make each instruction simple and unambiguous Example: Cut chicken into pieces and brown the pieces on all sides in a casserole dish in hot olive oil. Cut chicken into pieces. Heat olive oil in a casserole dish. Brown the chicken pieces in the casserole dish.

29 29 Instruction (Primitives) When writing an algorithm, make the instructions simple and unambiguous. Example: Cut chicken into pieces and brown the pieces on all sides in a casserole dish in hot olive oil. Cut chicken into pieces. Heat olive oil in a casserole dish. Brown the chicken pieces in the casserole dish. A “sequence” of simple instructions

30 30 Summary Problem Solving Process Algorithms Components of Algorithms –Values and Variables –Instructions –to be continued... Reading Bronson, Ch 1 and Ch 2


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