1. Mark Dixon, SoCCE SOFT 131Page 1 04 – Information Processing: Expressions, Operators & Functions

2. Mark Dixon, SoCCE SOFT 131Page 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. Mark Dixon, SoCCE SOFT 131Page 3 Questions: Properties Consider the following code: a) How many unique properties 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. Mark Dixon, SoCCE SOFT 131Page 4 Questions: Keywords Consider the following code: a) How many unique keywords 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. Mark Dixon, SoCCE SOFT 131Page 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. Mark Dixon, SoCCE SOFT 131Page 6 Information Processing All computing problems: –involve processing information/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 Input DataProcessOutput Data 9 7 63*

7. Mark Dixon, SoCCE SOFT 131Page 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. Mark Dixon, SoCCE SOFT 131Page 8 Example: Multiply Sub btnMultiply_OnClick() lblResult.InnerText = txtNum1.Value * txtNum2.Value End Sub

9. Mark Dixon, SoCCE SOFT 131Page 9 Operators Sit between the data 5 + 2 addition operatorresult is 7 5 - 2 subtraction operatorresult is 3 5 * 2 multiplication operatorresult is 10 5 / 2 division operatorresult is 2.5 "5" & "2" string concatenationresult is "52" work with objects: txtNum1.Value * txtNum2.Value

10. Mark Dixon, SoCCE SOFT 131Page 10 The following assignment statement: lblResult.InnerText = txtNum1.Value * txtNum2.Value contains an expression Expressions 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. Mark Dixon, SoCCE SOFT 131Page 11 Example: AddNum v1 Sub btnAdd_OnClick() lblResult.InnerText = txtNum1.Value + txtNum2.Value End Sub

12. Mark Dixon, SoCCE SOFT 131Page 12 Types of Information Numbers (numeric)29 (integer/whole) 56.23 (decimal/real) Text (string)"Hello there!" "BOO" Pictures Sound

13. Mark Dixon, SoCCE SOFT 131Page 13 AddNum problem The + operator works with: –numbers, and –text Text input boxes store text 23 + 16 = 39 "23" + "16" = "2316"

14. Mark Dixon, SoCCE SOFT 131Page 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) Parameter(s) Result SQR Function (16)4

15. Mark Dixon, SoCCE SOFT 131Page 15 Functions (cont.) Functions: come before the data (which is in brackets) Sqr(16) square rootresult is 4 Abs(-23) absolute valueresult is 23 Int(2.543) integerresult is 2 CInt("63") integer convertresult is 63 Left("boo",2) left stringresult is "bo" Right("hello",3) right stringresult is "llo" Mid("hello",2,2) middle stringresult is "el"

16. Mark Dixon, SoCCE SOFT 131Page 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. Mark Dixon, SoCCE SOFT 131Page 17 Example: AddNum v2 Sub btnAdd_OnClick() lblResult.InnerText = CInt (txtNum1.Value) + CInt (txtNum2.Value) End Sub

18. Mark Dixon, SoCCE SOFT 131Page 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. Mark Dixon, SoCCE SOFT 131Page 19 Hello Sub btnHello_ OnCluck () lblHello. inerText = "Hello" End Sub Computer –just symbol matching –No intelligence Example: Hello Errors missing nn: syntax error u instead of i: logical error (button does nothing)

20. Mark Dixon, SoCCE SOFT 131Page 20 Questions: Errors The following example is from lecture 1, –Spot the errors (you should find 6), and –decide whether they are syntax or logical Hello Sub btnBlue_OnCluck() document.bgColor = "Red" End Sub Sub btnRed_Onlick() document.bgColor "Red" End Sub Sub window_OnClick() document.bgColour = "White" End Sib

21. Mark Dixon, SoCCE SOFT 131Page 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