## Chapter 3 – Looping ### Using FOR, TO and NEXT Suppose you want to input five numbers and add them together. One way (don't type this in unless you are feeling dutiful) is to write: ``` 10 total=0 20 INPUT a 30 total+=a 40 INPUT a 50 total+=a 60 INPUT a 70 total+=a 80 INPUT a 90 total+=a 100 INPUT a 110 total+=a 120 PRINT total ``` This method is not good programming practice. It may be just about controllable for five numbers, but you can imagine how tedious a program like this to add ten numbers would be, and to add a hundred would be just impossible. Much better is to set up a variable to count up to **5** and then stop the program, like this (which you should type in): ``` 10 total,count=0,1 20 INPUT a 30 REM count=number of times that a has been input so far 40 total += a 50 count += 1 60 IF count <= 5 THEN GO TO 20 70 PRINT total ``` Notice how easy it would be to change line 60 so that this program adds ten numbers, or even a hundred. This sort of counting is so useful that there are two special keywords to make it easier: **FOR** and **NEXT** that are always used together. Using these, the program you have just typed in does exactly the same as: ``` 10 total = 0 20 FOR count = 1 TO 5 30 INPUT a 40 ;count=number of times that a has been input so far 50 total += a 60 NEXT count ```