BEGIN   UNTIL   BEGIN AGAIN   BEGIN WHILE REPEAT

BEGIN..UNTIL

In a BEGIN..UNTIL loop, the definition part located between these two words are repeated as long as the previous test result UNTIL delivers a false Boolean flag. Example:

: DACTYLO ( --)
    BEGIN
        KEY DUP EMIT
        ASCII $ =
    UNTIL ;

Running DACTYLO displays all characters typed on the keyboard. Only pressing the key marked with '$' can interrupt the repetition.

BEGIN..AGAIN

The use of AGAIN equals BEGIN ... 0 UNTIL.

BEGIN..WHILE..REPEAT

In this structure, the test runs before WHILE. If the result is false, execution continues after REPEAT . If the result is true, the definition part between WHILE and REPEAT is executed, then REPEAT performs an unconditional backward connection, ie returns execution to BEGIN.