February 25, 2010

 The BDE(Begin-During-End) event.  Worksheet – Exercise # 9 Instructions  2nd Period Test

In a While statement, actions occur while some condition remains true. Sometimes, we would like to make an action occur when the condition becomes false and the loop ends. The problem is how to make actions repeat (within a loop) but also make an action occur each time the loop ends? The answer is Use an BDE (Begin-During-End) event!

 Alice has a built-in While statement event for linking events to repeated actions. Select a While something is true event from the pull- down menu causes a While event block to be added to the Events editor.  This will block contains a Begin-During-End (BDE) block that allows you to specify what happens when the loop begins, during execution of the loop, and when the loop ends.

You need the following information:  A conditional expression (evaluates to true or false)  Begin – A method or instructions that is to be done once, at the time it becomes true.  During – A method or instructions that is to be done repeatedly, as long as the condition remains true.  End – A method or instructions that is to be done once, at the time the condition becomes false.

 Finish today’s worksheet.  You also have yesterday’s worksheet.  Test on Chapter 7 will be 2 nd period. Get ready!