function Presentation(auto,max,prefix,timing){
	this.auto=auto;	//	auto means on
	this.counter=0;
	this.prefix=prefix;
	this.max=max;
	this.timing=timing;
}
Presentation.prototype.update =	//	setTimeout function
function (backward){
	status='==================== '+ this.counter;
	if (!backward){
		this.counter++;
	}	else	{
		this.counter--;
	}
	if (this.counter==1){
		targetArea=document.all.item('borderTable');
		if (targetArea){
			sourceArea=document.all.item('projector');
			if (sourceArea){
				targetArea.innerHTML=sourceArea.innerHTML;
			}
		}
	}
	targetArea=document.all.item('presentationArea');
	if (this.counter<1){ this.counter=this.max}
	if (this.counter>this.max){ this.counter=1}
	this.timeToNext=this.timing
	if (targetArea){
		sourceArea=document.all.item(this.prefix+this.counter);
		if (sourceArea){
			if (sourceArea.timer){
				this.timeToNext=sourceArea.timer;
			}
			targetArea.filters.revealTrans.apply();
			targetArea.innerHTML=sourceArea.innerHTML;
			targetArea.filters.revealTrans.play();
			//alert(this.counter+'source='+sourceArea.id);
			//status='presenting slide '+this.counter;
		}	else	{
			status=this.prefix+this.counter+' area not found'
		}
	}	else	{
		status='presentation area not found'
	}
	if (this.handle){
		clearTimeout(this.handle);
	}
	if (this.auto){
		this.handle=setTimeout('theShow.update()',this.timeToNext);
	}
}
Presentation.prototype.startAgain=	//
function (){
	this.counter=0;
	this.update();
}
Presentation.prototype.startStop=	//
function (){
	if (this.auto){
		this.counter--;
		this.auto=false;
	}	else {
		this.auto=true;
	}
	this.update();
}
Presentation.prototype.moveBy=	//
function (by){
	this.counter=this.counter+by-1;
	this.update();
}