Type another number--perhaps I " and press RI l URN. PET will print the answer 35 and say READY. Your screen should look like this: numbers. But it you have 10 pairs of numbers, typing RUN each time can STILL he tedious! So, BASIC has two features which allows you to do an operation (in this case, add a pair of numbers) as many times as you like with out typing RUN. One of these features is the GOTO statement. It forces PET to GO TO a line you specify. instead of doing whatever it would normally do. (In this case, PET would normally stop and print READY when it finishes the sum.) You can do that with this statement:
150 GOTO 100 Now PET will print the sum, then go hack to line 100 and print the "E NTE R A NUMBER" message. Try it. Add up several pairs of numbers. When you're ready to go on, just press RETURN without having given PI :T any data (numbers) and it will jump out of your program and alt patiently for you to tell it what to do next. (You'll see PET's READY message and the flashing cursor.) The second feature is called a FOR-NE X T loop. It allows PET to perform an operation (or a sequence of operations) FOR as many times as you like. The word NEXT is the last line of the sequence, and tells PET that it has completed all the repeatable operations. Type these lines.
90 FOR I = 1 TO 10 150 NEXT I In this example. I is called the "index." PET keeps track of the number of times it performs the sequence of operations (lines 100 through 140) and keeps the count in the index. You set the index to l in statement 90 and tell PITT to count to 10. Everytime PET reaches statement 150 it increments, or adds to, the count, and goes hack to statement 90. Then PET checks to see if the number in the index is greater than the number of repeats you wanted. If it is, then PET looks for something else to do. If the count is less than or equal to the number of repeats (in this case, 10), it performs the whole sequence again.
In brief, PET will let you enter a pair of numbers FOR as many times as you request. And PET will do as much as you ask to each pair of numbers before going after the NEXT pair. Note that your PET automatically places the line numbers in ascending order, too. Using INPUT makes it easier to check the numbers, doesn't it'? Now you just type RUN, and each time you do so. yon can use different 28 www.commodore.ca Free for personal use but you must have written permission to reproduce 29