       10 // WHILE/ENDWHILE sample program
       20 //
       30 i:=10
       40 WHILE i>0 DO i:-1
       50 SYS assert, i=0
       60 //
       70 WHILE i<10 DO
       80   i:+1
       90 ENDWHILE
      100 SYS assert, i=10
      110 //
      120 PRINT "Ok"
