1 loops zdo while loop: yrepeats a block of code while a condition remains true do while condition...
TRANSCRIPT
1
Loops
Do While Loop: Repeats a block of code WHILE a
condition remains TRUE
Do While conditionCode to execute
Loop
2
Do While Loop (EXAMPLE):Dim count, sum as integercount = 1Do while count <= 3
sum = sum + val(Inputbox(“Number”, _
“Enter a Number”)count = count + 1
LoopText1.text = sum
3
Do While Loops
Starts with Do While statement and ends with the Loop statement
Requires a condition to be checked
Conditions can contain variables, constants, properties, functions, mathmetical operators, relational operators, logical operators
4
Do While Loops
The loop executes while the condition evaluates to TRUE, the loops terminates when the condition evaluates to FALSE
PRETEST LOOP --- evaluates the condition BEFORE any code is executed
5
Do While Loops
It is possible for the loop NOT to process any code at all --- if loop is false to start
YOU MUST CONTROL THE INCREMENT OF THE CONDITIONAL EXPRESSION or you can have an endless loop
6
Do While Loops
Example:Space Race with do while:Do while i1.top > 0 and i2.top > 0
Li_rnd1 = int((50 – 10 + 1) * rnd + 10)Li_rnd2 = int((50 – 10 + 1) * rnd + 10)I1.top = i1.top - li_rnd1I2.top = i2.top - li_rnd2
Loop
7
Do Until Loop
Repeats a block of code UNTIL a condition becomes TRUE
Do Code to execute
Loop Until condition
8
Example:Dim count, sum as integercount = 1Do
sum = sum + val(Inputbox(“Number”, _
“Enter a Number”)count = count + 1
Loop until count > 3
9
Do Until Loop
Begins with the Do statement and ends with the Loop until Statement
Requires a condition to be checked
Conditions can contain variables, constants, properties, functions, mathmetical operators, relational operators, logical operators
10
Do Until Loop
The loop executes while the condition evaluates to FALSE, the loops terminates when the condition evaluates to TRUE
POSTTEST LOOP --- evaluates the condition AFTER any code is executed
11
Do Until Loop
This loop processes the code at least ONCE
YOU MUST CONTROL THE INCREMENT OF THE CONDITIONAL EXPRESSION or you can have an endless loop
12
Accumulators and Counters (with do while & until loops)
Used to calculate subtotals, totals and averages
Counter --- numeric variable used for counting something (number of employees paid in a week)
accumulator --- numeric value used to adding together something (total dollar amount of a week’s payroll)
13
Accumulators and Counters (with do while & until loops)
initializing --- means to assign a beginning value to the counter or accumulator (start values are usually ZERO)
incrementing --- means adding to the counter or accumulator
14
Example of do while and do until using counters and accumulators:
CALCULATE THE AVERAGE SALES ENTERED BY A USER
User clicks “do while” or “do until” CB and a series of input boxes are produced until they cancel out of the input box. The average of the sales entered is displayed on the form
15
Example of do while and do until using counters and accumulators:
DO WHILE:Private Sub cmdWhile_Click() Dim strSales As String Dim intNumSales As Integer 'counter Dim sngSumSales As Single 'accumulator Dim sngAvgSales As Single strSales = InputBox("Enter a sales amount.
Click Cancel when finished.", "Input")
16
Example of do while and do until using counters and accumulators:
Do While strSales <> "" intNumSales = intNumSales + 1
'update counter sngSumSales = sngSumSales +
Val(strSales) 'update accumulator strSales = InputBox("Enter a sales
amount. Click Cancel when finished.", "Input")
Loop
17
Example of do while and do until using counters and accumulators:
sngAvgSales = sngSumSales / intNumSales lblAvg.Caption = Format(sngAvgSales,
"currency")
End Sub
18
Example of do while and do until using counters and accumulators:
DO UNTIL:Private Sub cmdUntil_Click() Dim strSales As String Dim intNumSales As Integer 'counter Dim sngSumSales As Single 'accumulator Dim sngAvgSales As Single strSales = InputBox("Enter a sales amount.
Click Cancel when finished.", "Input")
19
Example of do while and do until using counters and accumulators:
DO UNTIL:
Do intNumSales = intNumSales + 1
'update counter sngSumSales = sngSumSales +
Val(strSales) 'update accumulator strSales = InputBox("Enter a sales
amount. Click Cancel when finished.", "Input")
Loop Until strSales = ""
20
Example of do while and do until using counters and accumulators:
DO UNTIL:
sngAvgSales = sngSumSales / intNumSales lblAvg.Caption = Format(sngAvgSales,
"currency")
End Sub