To implement the iteration structure you can use a for while or statement
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You can use the iterative statement structure to perform the same statement or group of statements repeatedly while a condition is true. This type of flow control is also referred to as "looping". You can use a loop in your script to perform a sequence of statements several times. A loop essentially shortens the number of statements required. Looping provides a way to determine the number of repetitions automatically, based on evaluations made in your script. Show
The While-EndWhile Statement Structure You use the While-EndWhile statement structure to perform Looping. A While Loop repeats or loops WHILE a condition is true. A While loop consists of three parts: JAWS performs all statements within the boundaries of the While and EndWhile key words repeatedly until the condition in the While statement becomes false. Example 1: While-EndWhile loop structure Var In the above example, JAWS performs the While loop while iCount is less than five. Once the value of iCount becomes equal to 5, the loop ends and no further processing occurs. The For-EndFor Statement StructureAnother method of performing looping in your scripts is by using the For-EndFor looping statements. Similar to a While loop, a For loop consists of three parts: the keyword For that starts the loop, the condition being tested, and the EndFor keyword that terminates the loop. JAWS performs all statements found in the boundaries of the loop as long as the loop condition is true. An example of the syntax of a For loop follows.For x = Start to End...Statements to be performed go hereEndFor (adsbygoogle = window.adsbygoogle || []).push({}); The value of x must be an integer variable and the values of Start and End must be integers, integer variables, or integer constants. The major difference between the While and For looping structures is that a For loop will run a predetermined number of times. An example of the use of a For loop follows.Varint iCounterFor iCounter = 1 to 10; Loop will execute 10 timesSayInteger(iCounter); Speak the value of the iCounter variableEndForIn the above example the For loop will execute ten times. As set by the For statement, the iCounter variable starts with a value of 1 and increments by 1 each time the loop executes. Notice that the iCounter variable is automatically incremented each time the loop executes. At the end of the tenth loop iteration the value of icounter becomes 11 and the For statement is no longer true thus ending the loop. Each time the loop executes the SayInteger function speaks the value of iCounter. When this script is run you will hear JAWS count from one to ten.NOTE: Since a loop continues until a condition becomes false, you must be careful not to set up a loop with a condition that will never become false. To do so would create an infinite loop, which will cycle forever, and lock up the computer until the program is terminated manually. Think carefully about the condition meant to terminate the loop to be sure it will become false at some time. If you find that the computer seems to lock up after you execute a new script with a While loop in it, this is probably what is happening. For loops are less likely to cause an infinite loop because beginning and ending values are explicitly set in the For statement.Avoiding Infinite LoopsWhen you use a While loop in your script, care should be taken not to create an infinite loop. An infinite loop occurs when the condition in the While statement is not satisfied. The loop will continue to run until you manually end the program. This often causes a computer to lock up and may require the computer be restarted. Since JAWS performs a loop until a condition is met, you must be certain that the condition being tested can be satisfied. One way to avoid this problem while designing While loops is to include statements designed to end the loop after a certain number of repetitions. Example 2: Ending a loop after a certain number of iterationsVar In the above example, the iSafety variable is initialized to the value of 1.
A second example of the use of the While statement follows. This example could be used to move down through a menu until a specific item is found. Example 3: Looping through a menuVar In the above example, two variables are set before the While loop begins.
If running the above script, it is possible JAWS could end up in an infinite loop. If the file menu does not have an option with the word, "Open" in it, the value of the iExitLoop variable will never be set to one. This means the While statement will always be true and the loop will never end. In order to prevent this from happening, we need to let the iExitLoop variable act as a counter that will reach a certain value and cause the loop to end. Here is the example written again using a counter to insure the loop will end, even if the word, "Open" is not found in the menu. What statement is used to implement the iteration structure?The iteration statements repeatedly execute a statement or a block of statements. The for statement: executes its body while a specified Boolean expression evaluates to true . The foreach statement: enumerates the elements of a collection and executes its body for each element of the collection.
When might you choose to use a for loop instead of a while loop?Use a for loop when you know the loop should execute n times. Use a while loop for reading a file into a variable. Use a while loop when asking for user input. Use a while loop when the increment value is nonstandard.
What are the 3 main types of iterative structures?Iterative Control: LOOP and EXIT Statements. LOOP statements let you execute a sequence of statements multiple times. There are three forms of LOOP statements: LOOP , WHILE-LOOP , and FOR-LOOP .
Is for loop used for iteration?For-loops are typically used when the number of iterations is known before entering the loop. For-loops can be thought of as shorthands for while-loops which increment and test a loop variable.
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