These are common terminology in Forth and other computer languages with a stack.
- peek or tos
- Examine top of stack. (... x y tos gives you y and keeps the stack)
- push
- Add element to top of stack; other elements are pushed down. (... x push y makes the stack ... x y)
- pop
- Remove element from top of stack. ( ... x y pop makes the stack ... x)
- swap
- Swap top two stack elements. (... x y swap makes the stack ... y x)
- rot
- "Rotate" top 3 elements, bringing third element to top of stack. (... x y z rot makes the stack ... y z x)
- unrot
- "Rotate" top 3 elements in other direction. (... x y z unrot makes the stack ... z x y)
- dup
- Duplicate top stack element. (... x dup makes the stack ... x x)
- over
- Duplicate second stack element over top of stack. (... x y over makes the stack ... x y x; equivalent to swap dup unrot)
- nip, tuck, pick, ...
- Over the years, Forth programmers invented many more useful operations!