the innermost loop. Note that in such cases, only the final **EXIT** statement can take the optional parameter. To illustrate, consider the following example: ``` 100 FOR i=1 TO 10 110 FOR j=1 TO 10 120 PRINT i,j 130 IF j*i>80 THEN EXIT:EXIT 170 140 NEXT j 150 NEXT i 160 STOP 170 PRINT "Product exceeded 80":STOP ``` Note that when in a loop that exists within a procedure and/or subroutine, it is acceptable to use **ENDPROC** or **RETURN** as a legitimate way to exit said loop. ### REPEAT ... REPEAT UNTIL loops *NextBASIC* has another way of looping: a set of commands (or rather a single command block) called **REPEAT … REPEAT UNTIL**. You will have noticed that **FOR … NEXT** relies on counting to control the loop however you can also use a condition to control a loop. This type of loop begins with a **REPEAT** statement to indicate the beginning of the loop and a **REPEAT UNTIL** statement at the end, which also contains the condition to exit the loop. Try this: ``` 10 REPEAT 20 INPUT "Enter a number, or enter -1 to stop > ";n 30 PRINT n 40 REPEAT UNTIL n=-1 50 PRINT "Thank you!" ``` This program will keep accepting numbers and printing them, until you type -1 when it will politely thank you for your numbers. In a **REPEAT … REPEAT UNTIL** loop, everything between the **REPEAT** and the **REPEAT UNTIL** command will be executed (in this case, this would be lines 20 and 30), until the condition in the **REPEAT UNTIL** statement becomes *true* (in this case, that the number you have entered is **-1**). Note that because the condition is checked at the end, the block of statements will always execute at least once.\ The following, for example, would print an erroneous statement: ``` 10 x=1 20 REPEAT 30 PRINT "x is ";x;" but isn't 1" 40 REPEAT UNTIL x=1 50 PRINT "x is now 1." ``` Because line 30 is executed before the condition is checked at line 40, the message **x is 1, but it isn't 1** will still be printed, which is clearly wrong. Like a **FOR … NEXT** loop, you can also nest **REPEAT** loops, if you need to. So: ``` 10 n=1 20 REPEAT 30 PRINT "Counting to ";n 40 c=1 50 REPEAT 60 PRINT c;", "; ```