OK Aside from programming styles

Is there any "functional" difference between

WHILE expression DO    and     IF NOT(expression) THEN EXIT
and
UNTIL expression DO    and     IF expression THEN EXIT


First I thought that the DO/WHILE would activate as soon as
the condition occurred and drop out of a loop, but that is not
the case, the condition has to be active AND control has to be
back at the WHILE statement.


Example:

0001: CTR=0
0002: LOOP
0003:   CTR=CTR+1
0004:   WHILE CTR<4 DO
0005:   PRINT CTR
0006:   CTR=CTR+1
0007:   PRINT CTR
0008:   CTR=CTR+1
0009:   PRINT CTR
0010:   CTR=CTR+1
0011:   PRINT CTR
0012:   CTR=CTR+1
0013:   PRINT CTR
0014:   CTR=CTR+1
0015:   PRINT CTR
0016:   CTR=CTR+1
0017:   PRINT CTR
0018: REPEAT
0019: STOP
0020: END

My first thought was that once CTR = 5, the loop would end (at LINE 12) but it
didn't
until control was passed back to LINE 4, then it ended.
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