MELJUN CORTES Looping Structure

7/27/2019 MELJUN CORTES Looping Structure

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Looping Structure

Rommel Dorin

MELJUN CORTES



Testing Data



Keypress



Explained

KeyChar property to determinethe pressed key. (KeyChar

stands for "key character.") You

then use the e parameter's

Handled property to cancel the

pressed key if it is aninappropriate one. Example

shows using the KeyChar and

Handled properties in the

KeyPress event procedure.

Notice that you refer to the

Backspace key on a computer keyboard using the

ControlChars.Back constant.

The Backspace key is necessary

for editing the text box entry.



Looping

• The condition is evaluated with each

repetition (or iteration) of the loop and can

be phrased in one of two ways: It can

specify either the requirement for repeating the instructions or the

requirement for not repeating them .



Looping

• The requirement for repeating the

instructions is referred to as the looping

condition, because it indicates when the

computer should continue “looping” through the instructions.

• The requirement for not repeating the

instructions is referred to as the loop exitcondition, because it tells the computer

when to exit (or stop) the loop.



Looping

• A repetition structure can be either a pretest

loop or a posttest loop.

• In a pretest loop, the loop condition is

evaluated before the instructions within theloop are processed.

• In a posttest loop, the evaluation occurs after

the instructions within the loop areprocessed. Depending on the result of the

evaluation, the instructions in a pretest loop

may never be processed.



Do…Loop



For Next Loop

•For . . . Next loops are usually usedwhen you know the number of

times you want to repeat a loop.

The top of the loop is marked witha For statement and Next marksthe end of the loop. For loops use

a counter to keep track of times itruns.



For Next Loop



Counting Loops



For…Next Loop



For…Next Loop Flowchart



Step Parameter

• The Step parameter determineshow fast you move through a

loop.

• For loops can use positive and

negative numbers, and they can

also change by decimal values.



Loop Control Variables

•The numeric variable that

controls a For . . . Next loop

increments until it’s larger than its limit. (If it steps

backward, it decrementsuntil it’s smaller than its limit.)



Do While Loops

• For . . . Next loop is controlled by a

numeric variable

• While loop can be controlled with astring, a Boolean, or a numeric

variable.



Do While Loops

Syntax:



Counting Loops

• A While loop can mimic a For . . . Nextloop. It can be initialized to any value,

increment or decrement as needed,

and end when a specified value is

reached.



Counting Loops

i = 1

Do While i<= 5

rtbOut.AppendText(i.ToString & vbNewLine)

i = i+1

Loop



Do Loop While



Sentinel Values

• Sentinel values are set with each tripthrough the loop.

• As soon as that value makes the

condition False, the loop ends.



Do While – Example 1



Do Until Loops

Syntax:



Do Loop While

There’s a variation on the While loop.Instead of putting the condition in the Do

line, the While condition is placed in the

Loop line.



Exit Statement



Example



Activity

• Depreciation Program

• Formula:



Activity



Rnd

• Rnd is short for random. It’s used to generate a

random number. Random numbers are great.

• Rnd generates a random number greater or

equal to 0 and less than 1. The range is 0 to.999999.

• Syntax:



ID Random Generator

MELJUN CORTES Looping Structure

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