Those T[], B[], and oldT[], keeps track of which stack you want, either stack1, stack2, and stack3.
If i chose stack1 to put an item, it pushes and is ok,but if i try to pop the item in which i put in stack1, it says stack empty. If i try to view what is inside the stack 1 2 3, i get stack 1 = the item i just pushed, stack 2 = the item i just pushed, and stack 3 = the item i just pushed, which is wrong because i only pushed an item in stack 1.