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Week 1 Part II

Week 1 Part II. Kyle Dewey. Overview. Lab The art of programming Basic data types Variable declaration and initialization Data representation. Lab 1. The Art of Programming. General Advice. Top-down programming: Start with the big picture and get more specific

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Week 1 Part II

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  1. Week 1 Part II • Kyle Dewey

  2. Overview • Lab • The art of programming • Basic data types • Variable declaration and initialization • Data representation

  3. Lab 1

  4. The Art of Programming

  5. General Advice • Top-down programming: Start with the big picture and get more specific • Bottom-up programming: work up to the big picture by glueing together smaller, existing pieces • Divide and conquer: break a problem up into individual piecs

  6. Top-Down Programming • Start general and gradually become specific, filling in the details as you go along

  7. Top-Down Make Sandwich

  8. Top-Down Make Sandwich Put Meat on Bread Put Sides Together

  9. Top-Down Make Sandwich Put Meat on Bread Put Sides Together Get Meat from Fridge Get Bread from Cabinet

  10. Top-Down Make Sandwich Put Meat on Bread Put Sides Together Get Meat from Fridge Get Bread from Cabinet Open Fridge... Open Cabinet...

  11. Bottom-Up Programming • Glue preexisting pieces together to derive a solution

  12. Bottom-Up Handlebars Chain Frame Gears Wheels

  13. Bottom-Up Handlebars Chain Bolt Frame Gears Wheels

  14. Bottom-Up Handlebars Chain Bolt Frame Gears Bolt Wheels

  15. Bottom-Up Handlebars Chain Oil Bolt Frame Gears Bolt Wheels

  16. Bottom-Up Handlebars Chain Chain Tool Oil Bolt Frame Gears Bolt Wheels

  17. Combination • printf / scanf are generally written once (preexisting) • A middle ground

  18. Divide and Conquer • Really part of top-down and bottom-up • Break a problem down into distinct subproblems, solve them individually, and finally combine them

  19. Divide and Conquer Program Input Output

  20. Divide and Conquer Subprogram 1 Input Output / Input Subprogram 2 Output

  21. Divide and Conquer Subprogram A Input Subprogram B Output / Input Subprogram 2 Output

  22. General Five Step Process • Problem Statement • Input / Output Description • Hand Example • Algorithm Development • Testing

  23. General Five Step Process • Problem Statement • Input / Output Description • Hand Example • Algorithm Development • Testing

  24. Problem Statement • What are we trying to solve? • (Believe it or not, real software often goes astray here arguably more than anywhere else)

  25. General Five Step Process • Problem Statement • Input / Output Description • Hand Example • Algorithm Development • Testing

  26. Input / Output Description • What are the program inputs and what are the outputs? Output 1 Input I Program Output 2 Input 2 (A miracle occurs)

  27. General Five Step Process • Problem Statement • Input / Output Description • Hand Example • Algorithm Development • Testing

  28. Hand Example • Do the problem by hand • See if you actually understand what must be done

  29. General Five Step Process • Problem Statement • Input / Output Description • Hand Example • Algorithm Development • Testing

  30. Algorithm Development • Steps needed to solve the problem • Ultimately involves writing code • “Days of coding can save you hours of planning”

  31. General Five Step Process • Problem Statement • Input / Output Description • Hand Example • Algorithm Development • Testing

  32. Testing • See if solution actually works • Important step! • “50% of our code is tests”

  33. TDD • Test-driven development • Write tests before code • Wildly popular right now • The point: testing is important!

  34. C

  35. hello.c

  36. Running Code • Via make / gcc / cc (compilation) • Via ch (interpretation)

  37. Compilation • Code is ultimately converted to a form the machine understands directly • The result runs as fast as the machine • Certain interdependencies not handled

  38. Object Files 1: somethingFromHere(); 2: somethingFromElsewhere(); 3: somethingElseFromHere(); somethingFromHere somethingFromElsewhere somethingElseFromHere

  39. Linking • Technically separate from compilation, but the two often get conflated • Connects different pieces of code together

  40. Linking somethingFromElsewhere somethingFromHere somethingElseFromHere

  41. Linking somethingFromHere somethingFromElsewhere somethingElseFromHere

  42. Overall Process Linking Compilation Source Code File #1 Object File #1 Executable Source Code File #2 Object File #2

  43. Question • Why separate compilation and linking?

  44. Interpretation • As with ch • A program that understands the language runs it directly • Runs as fast as the interpreter

  45. Questions • Why compile versus interpret? • Why interpret versus compile?

  46. Types

  47. Types • All data in C has a type • Types determine: • What can be done with the data • How much space they take up (as with the sizeof operator)

  48. Basic Types • int: Integers (i.e. 1, 2, 3...) • Come in both signed and unsigned forms • double: floating point numbers (i.e. 5.1, 7.8, 2.93, ...) • char: A character (i.e. a, b, c,...)

  49. Variables • A container for a value • Must have a type

  50. Variable Declaration • Telling the compiler that a variable with a given name and type can be used int myInteger; double myFloatingPoint; char myCharacter;

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