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04 – Data Types

04 – Data Types. Admin: On-line Quiz. Questions: Expressions. What is the result of: 10 * Int(3.1973265765) How many functions are in the following: Int(12.472) * Sqr(9) + 8 / 2 How many operators are in the following: Int(12.472) * Sqr(9) + 8 / 2

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04 – Data Types

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  1. 04 – Data Types

  2. Admin: On-line Quiz

  3. Questions: Expressions • What is the result of: 10 * Int(3.1973265765) • How many functions are in the following:Int(12.472) * Sqr(9) + 8 / 2 • How many operators are in the following:Int(12.472) * Sqr(9) + 8 / 2 • Write an expression to: divide 15 by 3 and multiply the result by 6 30 2 3 (15 / 3) * 6

  4. Session Aims & Objectives • Aims • to introduce the idea of types of data • Objectives,by end of this week’s sessions, you should be able to: • recognise different types of data • numeric • string (text) • correct errors relating to data types

  5. Example: AddNum v1 <html> <head><title>Add Numbers</title></head> <body> <input type="text" id="txtNum1" /><br /> <input type="text" id="txtNum2" /><br /> <input type="button" id="btnAdd" value="Add" /> <p id="lblResult"></p> </body> </html> <script language="vbscript"> Sub btnAdd_OnClick() lblResult.InnerText = txtNum1.Value + txtNum2.Value End Sub </script> Doesn't work!

  6. Types of Information • Numeric (numbers) 29 (integer/whole) 56.23 (real/decimal) • String (text) "Hello there!" "BOO" • Pictures (numbers) • Sound (numbers)

  7. AddNum problem double quotes enclose text • The + operator works with: • numbers, and • text 23 + 16 39 "23" + "16" "2316" • Text input boxes store text: txtNum1.value + txtNum2.value • We need to convert text to numbers

  8. String Functions CInt("63") convert to integer result is 63Left("boo",2) left string result is "bo"Right("hello",3) right string result is "llo"Mid("hello",2,3) middle string result is "ell"Len("S Smith") length result is 7Space(5) spaces result is " "

  9. String Expressions

  10. String Expressions & Errors data data data operator operator ERROR! missing operator ERROR! missing data "What is " & txtN1.Value & " times " "What is twice " txtN1.Value & "?" "What is 6 minus " & & txtN1.Value & "?" "This is a number & txtN1.Value ERROR! missing "

  11. Questions: String Expressions • What is the result of:Mid("what is the time?", 3, 4) • What is the result of: Left("bob", 2) & Right("sal", 1) • Write an expression to:convert "16" to a number • Write an expression to:give the first two letters of "Mr John Smith" "at i" "bol" CInt("16") Left("Mr John Smith", 2)

  12. Example: AddNum v2 <html> <head><title>Add Numbers</title></head> <body> <input id="txtNum1" type="text" /><br /> <input id="txtNum2" type="text" /><br /> <input id="btnAdd" type="button" value="Add" /> <p id="lblResult"></p> </body> </html> <script language="vbscript"> Sub btnAdd_OnClick() lblResult.InnerText = CInt(txtNum1.Value) + CInt(txtNum2.Value) End Sub </script>

  13. Example: Sound <html> <head><title>Sound</title></head> <body> <object id="sndPlayer" classid="clsid:6BF52A52-394A-11d3-B153-00C04F79FAA6" style="width:0px; height:0px;"> </object> <input id="btnFart" type="button" value="Fart" /> </body> </html> <script language="vbscript"> Sub btnFart_onclick() sndPlayer.url = "Fart.wav" End Sub </script>

  14. Nested functions • nested functions (one inside another): Right(Left("Hello there", 5), 2) • do what is in the brackets first Right(Left("Hello there", 5), 2)= Right( "Hello" , 2)= "lo"

  15. Humans vs. Computers • Humans and Computers work very differently • Humans • declarative (goals): flexible sequence • intelligent: adaptive, questioning, rational • instinctive (without conscious thinking) • easily deal with incomplete and incorrect data • error prone (especially mundane repetitive tasks) • Computers • procedural / algorithmic: fixed sequence • do exactly what they are told • cannot deal with errors • no imagination or creativity

  16. Algorithms • algorithm: step-by-step sequence of instructions, to solve a problem • it describes how input data is to be processed in order to produce a desired output • recipe • ingredients (similar to data) • method (is a type of algorithm)

  17. Algorithms • Making a cup of tea: 1. Fill the kettle with water 2. Plug the kettle in 3. Switch the kettle on 4. Wait for the kettle to boil 5. Put water in cup 6. Put a tea bag into the cup 7. Add sugar to the cup 8. Add milk to the cup 9. Stir 10. Take the tea bag out

  18. What vs. How • problem solving • known problems (remember solution) • unfamiliar problems (creative process, imagination) • what vs. how: • What: increase value of a text box by 1 • How: • read the current value • add 1 • put the result back in the text box • For example: swap, search, sort

  19. Example: Swap v1 • put txtB into txtA • put txtA into txtB <html> <head><title>Swap</title></head> <body> <input id="txtA" type="text" value="Bob" /> <input id="txtB" type="text" value="Sally" /> <input id="btnSwap" type="button" value="Swap" /> </body> </html> <script language="vbscript"> Sub btnSwap_onclick() txtA.value = txtB.value txtB.value = txtA.value End Sub </script> • does not work!

  20. Example: Swap v1 (why?)

  21. Example: Swap v2 <html> <head><title>Swap</title></head> <body> <input id="txtA" type="text" value="Bob" /> <input id="txtB" type="text" value="Sally" /> <input id="btnSwap" type="button" value="Swap" /> <input id="txtTemp" type="text" disabled="disabled" /> </body> </html> <script language="vbscript"> Sub btnSwap_onclick() txtTemp.value = txtA.value txtA.value = txtB.value txtB.value = txtTemp.value End Sub </script> • put txtA into temp • put txtB into txtA • put temp into txtB • works!

  22. Example: Swap v2 (Why?)

  23. Example: Student Loan (Analysis) • What: Calculate annual student load repayment from salary • How: • Algorithm: • read annual salary • deduct £15000 • calculate 9% • display result

  24. Example: Student Loan (Design) • When Calculate button is clicked: • read annual salary text box • deduct £15000 • calculate 9% • put result in paragraph • Test Data: Input Process Output • £15000 15000-15000*0.09 = £0 • £16000 16000-15000*0.09 = £90

  25. Concrete vs. Abstract code • we have: • pixelLeft • pixelTop • right = left + width • middle = left + (width / 2) • concrete vs. abstract code: picBall.style.pixelLeft = 400 picBall.style.pixelLeft = document.body.clientWidth / 2 • first one only works when the window width is 800

  26. Generating Assignment Code • put "Hello" into txtAtxtA.value = "Hello" • get txtA and join it with txtB, and put the result in parResparRes.innerText = txtA.value + txtB.value • put into txtNum2, the result of multiplying txtNum1 by 2txtNum2.innerText = txtNum1.value * 2

  27. Questions: Assignment • What is the code for: • put 0 into the pixelLeft property of picHouse • increase the pixelTop property of picHouse by 5 • decrease the pixelTop property of picCar by 9 picHouse.style.pixelLeft = 0 picHouse.style.pixelTop = picHouse.style.pixelTop + 5 picCar.style.pixelTop = picCar.style.pixelTop - 9

  28. Errors • txtTemp.value = "" + 5 type mismatch (cannot add "" to 5) • txtTemp.value = "7" + 5 OK – VB converts "7" into 7 automatically

  29. Example: Text Shift <html> <head><title>Text Shift</title></head> <body> <p id="parH"></p> </body> </html> <script language="vbscript"> Sub Window_OnLoad() parH.innertext = "Hello There" & Space(100) Window.SetInterval "TextShift", 50 End Sub Sub TextShift() parH.innertext = Mid(parH.innertext,2) & Left(parH.innerText,1) End Sub </script>

  30. Tutorial Exercises: AddNum • LEARNING OBJECTIVE:use a function to convert string (text) to integer (number) data • Task 1: get the addnum examples (v1 and v2) working

  31. Tutorial Exercises: Swap • LEARNING OBJECTIVE:use an algorithm to solve a problem • Task 1: get the swap examples (v1 and v2) working • Task 2: change v2 of the swap page so that the temporary text box is hidden

  32. Tutorial Exercises: Student Loan • LEARNING OBJECTIVE:implement an algorithm in code • Task 1: Create the user interface (page design) for the Student Loan example (from the lecture), using HTML tags (you will need a text box, a button, and a paragraph). • Task 2: Add code that implements the following algorithm:When the Calculate button is clicked: • read annual salary text box • deduct £15000 • calculate 9% • put result in paragraph • Task 3: Modify your program so that it calculates and displays monthly income and repayment amounts (as well an annual).

  33. Tutorial Exercises: Text Shift • LEARNING OBJECTIVE:develop and implement an algorithm to solve a problemuse string manipulation functions, and sound • Task 1: get the Text Shift example (from the lecture) working • Task 2: modify your program so that the text goes the other way. • Task 3: modify your program so that a noise is made when the user moves the mouse over the text.

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