A new learning activity from Creative Computing.... Beginning With BASIC by William R. Morrison Curtis Jr. High School Sudbury, Massachusetts The act of sitting down at a computer terminal creates a closed world. Even first-time users become absorbed, lose track of time, and seek only to further whatever dialogue they are involved in. Can you remember the pleasures of getting the machine to do what you wanted it to? Or the frustrations of many error messages? These two activities are designed for junior-high school students to use as part of an introductory unit on computers. They are intended to help make that first experience informative; to let students learn step by step how the computer responds to various commands; and finally to let students form their own images of the computer as a partner in a dialogue. A. EXERCISES IN IMMEDIATE MODE This first guide takes the student from immediate mode to a simple program. It presents a minimum of rules, emphasizing instead a series of actions, and lets the student draw whatever conclusions he can. The impact of these first impressions will later be the foundation for a more formalized presentation, the objects of which should be familiar. Explanations tend to turn students off unless they have already had an experience that makes them eager to know why. Some Things to Try With a Computer that Speaks BASIC: 1. Try some PRINT statements: PRINT MY COMPUTER SPEAKS BASIC What happened? Did you forget something? Correct the command and try again. Will the computer accept something like: 2+5=4? Can you make it print such arithmetic nonsense? Now print your name and the date. 2. Try this: PRINT "SOME ARITHMETIC"; 22*33;35/7O;5-9,7+9 What happens when you use the ; or the ,? How does the computer handle fractions? Try a few, such as 1/3+5/8, and see. 3. Here is a short program. Type it in and try it out. 10 INPUT A 20 INPUT B 30 PRINT A "TIMES" B "IS" A*B 40 GOTO 10 If something went wrong, remember that everything you type in has meaning to the computer, every quote mark, comma, etc. 4. Let's make some changes and see how this program can be improved. You don't have to type the whole thing over again, of course; change the lines by typing the line number and its line. First, though, stop the computer from running the old program by typing CTRL/C. Change line 20: Type: 20 LET B=1 Change line 40: Type: 40 LET B=B+1 Add a line 50: Type: 50 GOTO 30 What happened to old line 20? Find out by asking the computer to LIST the program. Now, try a RUN of the program. Stop the program with CTRL/C - does CTRL/C stop the computer while it is LISTing a program? Give the program a title with: 5 PRINT "TlMES TABLE" Do you see why line numbers go up by 10's? Now make the program stop automatically when it gets to A times 10: 45 IF B=10 THEN 60 Of course you need line 6O! 60 STOP If B is not 1O, what does the computer do? 5. You should now have a program that asks for a number and then types out all the multiples of that number up to 10 times that number. Go ahead - pick a number and hand in a RUN and a LIST of the program. 6. Can you: a) Further change the program to add, subtract or divide instead of multiplying? b) Change the program to print the multiplications or divisions, etc., in a table form? c) (Difficult!) Make the computer print the table starting at 1 x 1, going to 1 x 1O, then starting over by itself at 2 x 1, 2 x 2, etc.?