/*
	So far our conditions have been "is this one thing true" but you may also want to sometimes test
	if more than one condition is true, or if at least one condition of several are true.
	
	Introducing AND and OR, or is it OR and AND?  We'll never know!  Well yes we will, read on for more...
	
*/
program AndOr;
var  
	val1, val2: byte; 	// Define two variables
   
begin
	// define the screenmemory pointer
	definescreen();
	
	// clear the screen and colour memory
	clearscreen(32, screen_char_loc);
	clearscreen(WHITE, screen_col_loc);
	
	// Set the screenmemory pointer to point to the screen memory:
	screenmemory := screen_char_loc;

	// lets set the val1 and val2 variables to some values we can test with:
	val1 := 10;
	val2 := 20;
	
	// Using AND we can test for two or more conditions, all of which must be true for the PrintString to execute:
	if (val1 = 10 and val2 = 20) then printstring("BOTH CONDITIONS ARE TRUE!",0,40);

	screenmemory := screenmemory + screen_width;	// move to next line on the screen

	// In contrast, one of these conditions is NOT true, so the PrintString will not execute in this instance:
	if (val1 = 20 and val2 = 20) then printstring("ONE CONDITION IS NOT TRUE!",0,40);
	
	screenmemory := screenmemory + screen_width;	// move to next line on the screen
	
	// Changing the AND to an OR means only one of the conditions must be true:
	if (val1 = 20 or val2 = 20) then printstring("ONE CONDITION IS TRUE!",0,40);

	screenmemory := screenmemory + screen_width;	// move to next line on the scree

	// Lets use two conditions to repeat while val1 and val2 are not the same, AND val1 is less than 14
	while (val1 <> val2 and val1 < 14) do
	begin
		screenmemory[val1] := 65;	// draw a spade for val1
		screenmemory[val2] := 83;	// draw a heart for val2
		val1 := val1 + 1;			// move val1 to the right
		val2 := val2 - 1;			// move val2 to the left
	end;
	// They stop before they meet - but which condidtion became false first?
	// (hint: it's val1 < 14)

	loop();
end.
