More Practice

Here is the program:

' Loop with a loop condition
'
LET COUNT = 0            'Statement 1

DO WHILE COUNT <= 5      'Statement 2
  PRINT COUNT            'Statement 3
  LET COUNT = COUNT + 1  'Statement 4
LOOP 

END

It is often useful to try to understand the first number and the last number that are printed.

• When the program starts, COUNT is set to zero (Statement 1), the DO statement (Statement 2) lets the loop body start, and the PRINT statement (Statement 3) prints 0.
• The program runs for a while, counting COUNT up from 0 to 1, from 1 to 2, from 2 to 3, from 3 to 4...
• Eventually COUNT becomes 4 and is printed. Now Statement 4 changes COUNT from 4 to 5. Then the DO statement (Statement 2) lets the loop body start since 5 is equal to 5, and the PRINT statement (Statement 3) prints 5. Statement 4 changes COUNT from 5 to 6.
• COUNT is now 6, so the DO statement does NOT let the loop body begin again, so the END is executed and the program is over.

Getting confused by a loop is very easy, even among professional programmers. Practice helps. Here is the program again, with changes.

' Loop with loop condition
'
LET COUNT = 1            'Statement 1

DO WHILE COUNT <= 3      'Statement 2
  PRINT COUNT            'Statement 3
  LET COUNT = COUNT + 1  'Statement 4
LOOP 

END