It was thus said that the Great Zane H. Healy once stated: One other thing about Forth---white space is *very* important and identifiers ... okay, two things about Forth, white space is *very* important, identifiers can contain *any* printable character and it's ... okay three things about Forth, white space is *very* important, identifiers can contain *any* printable character, it's stack based and ... Oh drat it all. Let's start over again ... White space is very important since anything that *isn't* white space is taken as a token and used to look up the current meaning. ." is a typical Forth word that prints anything past it up to the next double quote. In fact, it's perfectly legal to do: : 2 1 ; to redefine the sequence `2' to push the value 1 onto the stack (normally, if a space delimited token isn't found, Forth will then attempt to convert it (using the current base) into a number, and if that fails, then you get an undefined error message (which is what is happening to you above). Some systems actually do define: : 0 0 ; : 1 1 ; : 2 2 ; as that is slightly faster and takes less space than storing a literal number in the internal representation (although that really depends upon the Forth system). -spc (Bring out the comfy chair ... )