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04 – Information Processing: Expressions, Operators & Functions

04 – Information Processing: Expressions, Operators & Functions. Questions: Events. Consider the following code: a) How many unique events does it contain? b) Name the event(s ). Sub btnAns_OnClick() If txtAns.Value = 15 Then document.bgcolor = "yellow"

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04 – Information Processing: Expressions, Operators & Functions

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  1. 04 – Information Processing:Expressions, Operators & Functions

  2. Questions: Events • Consider the following code: a) How many unique events does it contain? b) Name the event(s). Sub btnAns_OnClick() If txtAns.Value = 15 Then document.bgcolor = "yellow" lblComment.innertext = "Correct, well done!" Else document.bgcolor = "cyan" lblComment.innertext = "Sorry, try again" End If End Sub 1 Click OnClick

  3. Questions: Properties • Consider the following code: a) How many uniqueproperties does it contain? b) Name the properties. Sub btnAns_OnClick() If txtAns.Value = 15 Then document.bgcolor = "yellow" lblComment.innertext = "Correct, well done!" Else document.bgcolor = "cyan" lblComment.innertext = "Sorry, try again" End If End Sub 3 value, bgcolor, & innertext

  4. Questions: Keywords • Consider the following code: a) How many uniquekeywords does it contain? b) Name the keywords. Sub btnAns_OnClick() If txtAns.Value = 15 Then document.bgcolor = "yellow" lblComment.innertext = "Correct, well done!" Else document.bgcolor = "cyan" lblComment.innertext = "Sorry, try again" End If End Sub 5 Sub, If, Then, Else, & End

  5. Session Aims & Objectives • Aims • Introduce you to main processing concepts, i.e. expressions, operators and functions • Objectives,by end of this week’s sessions, you should be able to: • evaluate expressions • assign a value to a object's property, • using combination of literal values, operators, functions, and identifiers

  6. Information Processing Input Data Process Output Data 7 * 63 9 • All computing problems: • involve processinginformation/data • information has meaning (e.g. 5lb 3.3kg 18 years) • data has no meaning (e.g 5 3.3 18) • following this pattern: • For example: • to multiply two numbers: 7 * 9 = 63

  7. Information Processing (cont.) • Hence, to solve any computing problem ask: • what information goes in • what processing is done to it • what information comes out

  8. Example: Multiply <html> <head> <title></title> <script language="VBScript"> Sub btnMultiply_OnClick() lblResult.InnerText = txtNum1.Value * txtNum2.Value End Sub </script> </head> <body> <input type="text" ID=txtNum1> <input type="text" ID=txtNum2> <input type="button" ID=btnMultiply value="Multiply"> <p ID=lblResult> </body> </html>

  9. Operators • Sit between the data5 + 2 addition operator result is 7 5 - 2 subtraction operator result is 3 5 * 2 multiplication operator result is 10 5 / 2 division operator result is 2.5 "5" & "2" string concatenation result is "52" • work with objects:txtNum1.Value * txtNum2.Value

  10. Expressions • The following assignmentstatement:lblResult.InnerText = txtNum1.Value * txtNum2.Value contains an expression • Given: txtNum1.Value = "7",txtNum2.Value = "9"can evaluate expression:lblResult.InnerText = txtNum1.Value * txtNum2.Value(from above)lblResult.InnerText = "7" * "9" (substitute)lblResult.InnerText = 63 (calculate) Animation

  11. Example: AddNum v1 <html> <head> <title></title> <script language="VBScript"> Sub btnAdd_OnClick() lblResult.InnerText = txtNum1.Value + txtNum2.Value End Sub </script> </head> <body> <input type="text" ID=txtNum1> <input type="text" ID=txtNum2> <input type="button" ID=btnAdd value="Add"> <p ID=lblResult> </body> </html>

  12. Types of Information • Numbers (numeric) 29 (integer/whole) 56.23 (decimal/real) • Text (string) "Hello there!" "BOO" • Pictures • Sound

  13. AddNum problem • The + operator works with: • numbers, and • text • Text input boxes store text 23 + 16 = 39 "23" + "16" = "2316"

  14. Functions & Operators • Used to: • process (manipulate) data • Both Functions & Operators: • take input data/parameters (1 or more item) • process it • return a result • which replaces the expression (substitution) Function Parameter(s) Result SQR (16) 4

  15. Functions (cont.) • Functions: come before the data (which is in brackets)Sqr(16) square root result is 4Abs(-23) absolute value result is 23Int(2.543) integer result is 2CInt("63") integer convert result is 63Left("boo",2) left string result is "bo"Right("hello",3) right string result is "llo"Mid("hello",2,2) middle string result is "el"

  16. Questions: Expressions • What is the result of: 1 + CInt("23") + Int(2.76786) + Sqr(Int(9.4523)) • What is the result of: "23" & "18" + Left("bob",1) + Right("sal",2) • Write an expression to:give integer value of "16.7658765" • Write an expression to:give the first two letters of "Mr John Smith" 1 + 23 + 2 + 3 = 29 "23" & "18" & "b" & "al" = "2318bal" Int(CInt("16.7658765")) Left("Mr John Smith", 2)

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

  18. Testing & Debugging: Errors • 3 error types : • syntax: computer unable to understand your instructions (program does not execute), e.g. • variable not defined (probably most common) • run-time: program can't execute instruction and exits (future lecture) • Device unavailable (e.g. floppy drive) • logical: program executes but does not not match specification (do what was intended), e.g. • clicking on button does nothing, when you thought you attached code to it • clicking on blue button changes colour to red (when it should change to blue)

  19. Example: Hello Errors u instead of i: logical error(button does nothing) missing nn: syntax error <html> <head> <title>Hello</title> <script language="VBScript"> Sub btnHello_OnCluck() lblHello.inerText = "Hello" End Sub </script> </head> <body> <input type=button ID=btnHello Value="Hello"> <p ID=lblHello> </body> </html> • Computer • just symbol matching • No intelligence

  20. Questions: Errors <html> <head> <title>Hello</title> <script language="VBScript"> Sub btnBlue_OnCluck() document.bgColor = "Red" End Sub Sub btnRed_Onlick() document.bgColor "Red" End Sub Sub window_OnClick() document.bgColour = "White" End Sib </script> </head> <body> <input type=button ID=btnRed Value="Red"> <input type=button ID=btnBlue Value="Blue"> <p ID=lblHello> </body> </html> • The following example is from lecture 1, • Spot the errors (you should find 6), and • decide whether they are syntax or logical

  21. Tutorial Exercises • Task 1: get multiple example working • Task 2: get addnum examples (v1 and v2) working • Task 3: create a new page with two text boxes (surname and forenames), and a button (initials). When the button is clicked the first character from each text box (i.e. the person's initials) should be displayed. • Task 4: create a new page that helps the user covert from Pounds to Dollars

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