: UNTIL ( -- ) ?COMPILING
  COMADMIN@ BEGINADMIN ?PAIRS
  POSTPONE JOF
  HERE  0 ,
  OFFSET! ; IMMEDIATE

Remember that IF and BEGIN leave a message for THEN and UNTIL.

3. Unconditional branches

IF...THEN and BEGIN...UNTIL have counterparts, AHEAD...THEN and BEGIN...AGAIN, that use unconditional jumps. These words don't consume a flag, don't do tests and, at first blush, seem to be perfectly useless:

AHEAD ??? THEN ...
BEGIN ... AGAIN ???

AHEAD always jumps forward to THEN and AGAIN always jumps to BEGIN. Why the unreachable code ??? after AHEAD and after AGAIN ?

These structures only make sense when used in an unstructured way with other control structures.

... IF ... ELSE ... THEN ... can be seen as
... IF ... AHEAD THEN ... THEN where the first THEN matches IF and the second THEN matches AHEAD. In other words: wrongly nested. This can be made 'whole' again with a trick, if desired, when, exactly between AHEAD and THEN, the two compiler administration packets are switched.

A standard word to do this exists: 1 CS-ROLL

: ELSE (--)
  POSTPONE AHEAD 1 CS-ROLL
  POSTPONE THEN ; IMMEDIATE

The same trick can be used for AGAIN:

... BEGIN ... IF ... AGAIN THEN ... turns into
... BEGIN ... IF ... AGAIN? ... with

: AGAIN? ( -- )
  POSTPONE AGAIN 1 CS-ROLL
  POSTPONE THEN ; IMMEDIATE

However, a different solution for this specific problem exists. We'll tell you about it next time.