Negative Starting Value

The starting value of a FOR loop does not have to be positive. Here is the addition program again, with different start and finish:

' Add up the integers from START to FINISH
'
LET TOTAL = 0    ' TOTAL will hold the sum
LET START = -2
LET FINISH = 3
'
FOR COUNT = START TO FINISH
  LET TOTAL = TOTAL + COUNT
  PRINT COUNT, "has just been added to TOTAL which is now", TOTAL
NEXT COUNT
'
PRINT "The total is:", TOTAL
END

For now, ignore what happens to TOTAL and concentrate about what happens to COUNT. The FOR statement says to use values for COUNT of -2, -1, 0, 1, 2 and 3. Remember to include the zero, since zero is as good a number as any other.