Introduction To Programming (2009 2010)

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MUFIX Community Session

Name : Introduction To Programming
Speaker : Islam El-Hosary

Term 1 (2009-2010)

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Introduction To Programming (2009 2010)

  1. 1. Introduction to Programming “How to win friends and influence computers”
  2. 2. A Brief History of Computers General purpose minions Orders Human calculators Mechanical calculators Electronic calculators General purpose machines Programs
  3. 3. What Is Programming Programming is just telling a computer to do something, BUT Computers know very little and have no common sense what-so-ever, so your instructions have to be broken down to small, simple parts, AND Computers will do exactly what you tell them.
  4. 4. Basic Programming Programming at it’s core is about two things: defining problems, and solving problems. These two aspects are tightly integrated • To solve a problem you first must clearly know what it is • Clearly and completely defining a problem gets you a long ways towards a solution
  5. 5. Four Tools To Get Started Just getting started is often the hardest part of the project. Before diving in to the code, do the design document. Four tools to help are –Action/Event List –Flow Chart –Data Model –Iterative Refinement
  6. 6. Action List This is a good tool to use in applications that have user interaction. Write down each action the user can take. Add a bit of detail info to each action • Circumstances in which the user may take the action (1-3 sentences, and/or list) • What happens when they do the action (1-3 sentences) • What other actions this one allows and denies (list format)
  7. 7. Flow Charts Flow charts are a very useful tool to clarify and define programming problems • They delineate key points in your program • They’re especially good for state-based programs, such as web applications Don’t get too bogged down in details when creating a flow chart – stay high level
  8. 8. Data Model A data model is a detailed description of the information that the application will manipulate. Start with a general idea/concept, then break it down into smaller parts, and repeat. Aim for having each part be a string, a number, or a list or collection thereof.
  9. 9. Iterative Refinement - the Ur-Program The process of iterative refinement 2. Say what you want the computer to do 3. If it’s all in terms the computer will understand, then stop, you’re done 4. Otherwise, break each part into simpler steps 5. Go to step 2 NOTE: works for small children as well as computers
  10. 10. The Real World These are important concepts, and when done right you end up documenting your code as you go. HOWEVER… Real-world programming often doesn’t explicitly involve these techniques except at high levels in the design document. You should definitely use them there, and for actual coding keep them in mind as fallback strategies if your stuck on a problem.
  11. 11. What Computers Can Do Well
  12. 12. What Computers Can Do Well Doing the same things over and over Remembering things Mathematics, ‘regular’ and true / false Changing actions based on conditions Taking in information Sending out information
  13. 13. What Computers Can Do Well Doing the same things over and and Subroutines Loops over Remembering things Variables and Assignment Mathematics, ‘regular’ and true / falseOperators Statements Changing actions based on conditions Conditionals and Blocks Taking in information Sending out information Input Output
  14. 14. Statements, and Blocks A statement is a basic instruction for the computer Statements are executed in order, from first to last One or more statements may be grouped together into a block A block is marked by curly braces { and }
  15. 15. Loops A loop is a special kind of statement that tells a computer to repeat a given set of instructions A for-loop repeats a given number of times e.g. say “hi” five times: for (1..5) { say “hi” } A while-loop repeats as long as a certain condition is true e.g. go somewhere : while (not arrived) { take step }
  16. 16. Subroutines A subroutine, function or procedure is a block of statements that’s been given a name and which is executed when ever that name is used. Essentially, it’s a miniature sub-program that you can use in your larger program. Once a function finishes, the execution returns to the place from which it was called. Functions can take parameters, or arguments, which allow values to be sent into the block of code Functions can return values.
  17. 17. Variables A variable has a name, or identifier, and may have a value associated. Associate a given value with a given variable by making an assignment. Variables can be declared, which creates them without any value. Some languages require this.
  18. 18. Variable Names MUST: Start with a letter Contain letters or numbers or underscores SHOULD: Be meaningful (often 10+ characters) Be readable (use _ or mixCase to mark words) Follow convention (start lower case, i, x, y)
  19. 19. Basic Values Literal values: Numbers 0, -3, 8.223419783 Strings (a series of characters) “zero”, ”0”, “cheddar cheese” Expressions: One or more values, expressions, or variables combined by operators 8.3 * 4.291 2 “smoked” . “ “ . “cheddar” A variable used in a expression is replaced by its value ingredient_count + 3
  20. 20. Operators There are all the standard math operators + - * / % () The string concatenation operator combines two or more strings into one Depends on the language (often . or +) There are many other operators too Boolean math Comparisons Specialized Operators combine values and expressions into larger expressions
  21. 21. Conditionals A conditional, or branch, statement executes a block of other statements based on whether a given condition is true or false Conditions are evaluated using boolean operators, as well as comparisons and other things that are true or false
  22. 22. General Conditional Statement if (condition) Block executed if condition is true else if (other condition) Block executed if other condition is true else Block executed if all conditions are false
  23. 23. Input and Output Special statements get data into and out of a program. Details vary by language Data can come from: keyboard, web page, mouse, file, other Data can go to: screen, file, the internet, other
  24. 24. Comments Comments are a way to put text in the program code which does not get executed. This is very useful for leaving notes / descriptions / explanations, and for testing. Comments are usually denoted by # or // to comment to the end of the line /* to comment out multiple lines */
  25. 25. Best Practices Always make backups of original working code before messing with it Use comments to mark what you change, how, and when, and to keep copies of original statements Test early, test often Work together – more eyes means fewer bugs Read the manual – there are great references online Look at examples
  26. 26. mr.islamelhosary@gmail.com

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