1. The problem statement, all variables and given/known data In the book it gives following background for using threaded trees: "The concern is that some additional time has to be spent to maintain the stack & some more space has to be set aside for the stack itself." & then it says "It is more efficient to incorporate the stack as part of the tree. This is done by incorporating threads in a given node" From first sentence "It is more efficient to incorporate the stack as part of the tree" it looks as if stack is utilized in the threaded tree but i cant understand what it means " incorporate stack as part of tree" but in the next sentence it says "This is done by incorporating threads in a given node". By threads we mean pointers which point to the inorder successor & inoder predecessor. They are not stack. So this is my problem that i cant understand whether stack is used in a threaded tree or not 2. Relevant equations No equations, only theory. 3. The attempt at a solution I think stack is present but at the same time it has threads/pointers also which help in efficient traversal Some body please guide me. Zulfi.