Stack Manipulation
 2DROP

twodrop ( x1 x2  ), Drop cell pair x1 x2 from the stack.
 2DUP

twodupe ( x1 x2  x1 x2 x1 x2 ), Duplicate cell pair x1 x2.
 2OVER

twoover ( x1 x2 x3 x4  x1 x2 x3 x4 x1 x2 ), Copy cell pair x1 x2 to the top of the stack.
 2SWAP

twoswap ( x1 x2 x3 x4  x3 x4 x1 x2 ), Exchange the top two cell pairs.
 >R

tor

Interpretation: Interpretation semantics for this word are undefined.

Execution: ( x  ) ( R:  x )

Move x to the return stack.
 DEPTH

(  +n )

+n is the number of singlecell values contained in the data stack before +n was placed on the stack.
 ?DUP

questiondupe ( x  0  x x ), Duplicate x if it is nonzero.
 DROP

( x  ), Remove x from the stack.
 DUP

dupe ( x  x x ), Duplicate x.
 OVER

( x1 x2  x1 x2 x1 ), Place a copy of x1 on top of the stack.
 R>

rfrom

Interpretation: Interpretation semantics for this word are undefined.

Execution: (  x ) ( R: x  )

Move x from the return stack to the data stack.
 R@

rfetch

Interpretation: Interpretation semantics for this word are undefined.

Execution: (  x ) ( R: x  x )

Copy x from the return stack to the data stack.
 ROT

rote ( x1 x2 x3  x2 x3 x1 ), Rotate the top three stack entries.
 SWAP

( x1 x2  x2 x1 ), Exchange the top two stack items.