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QBASIC Programming for Kids

1. AS Hello QBASIC FOR I 1 to LEN AS PRINT LEFTS AS I NEXT I LENO is very useful when you want the user to provide the string Try this INPUT Enter a string AS PRINT The string you entered was LEN AS characters long CHRS and ASC Computers really only know about numbers To make strings of letters computers convert letters to numbers so they can work with them CHR and ASC let you do the same kinds of conversions CHRS converts a number to a character We ve already seen this in a previous chapter Try this FOR I 14 to 255 PRINT I CHRS I NEXT I That program displays all the character numbers from 14 through 255 followed by the characters that they represent CHR is very useful for getting characters that aren t on the keyboard Like this PRINT STRINGS 40 CHRS 1 There are some very interesting characters between CHR 1 and CHR 31 As an example CHR 7 makes a beep Try it PRINT CHRS 7 There are other interesting things as well Play around with CHR a bit and you ll find several ASC is the opposite of CHR ASC takes a character and tells you its number Try this PRINT ASC A That program prints 65 because the character code for a capital A is 65 The code that QBASIC uses to convert letters to numbers is called ASCII pronounced askee INSTRO INSTRQO lets you search for a string in another string If it f
2. LOOP Kind of messy but interesting How about a clock CLS DO LOCATE 1 1 PRINT TIMES SLEEP 1 LOOP TIMES is a special variable that contains the current time Press Break to stop Chapter 19 WIDTH Use WIDTH 40 for big text It changes the entire screen to wide text mode Use WIDTH 80 to go back to normal size text SCREEN 0 WIDTH 40 CLS PRINT Wow This is big INPUT Press lt Enter gt to go back A WIDTH 80 PRINT That s more like it Unfortunately you won t see the big text in a window You ll have to press lt Alt gt lt Enter gt to switch to full screen mode Be sure to press lt Alt gt lt Enter gt again to switch back to window mode Chapter 20 CHR There are many special symbols and other characters you can display that aren t on the keyboard Try this CLS PRINT CHR 1 CHRS 2 That prints a couple of smiley faces There are plenty of other characters too This program will show you many but not all of them CLS FOR I 32 to 255 PRINT I CHRS I NEXT I Chapter 21 Graphics So far we ve only been dealing with text words and numbers How do we do pictures in QBASIC First we need to use SCREEN to change from text mode to graphics mode SCREEN SCREEN lets you select a graphics screen instead of the text screen we ve been using This will let you draw pictures In the next program we ll use DR
3. Back in Chapter 4 we saw a DO LOOP that went forever There are a number of ways to make a loop stop One way is to use WHILE This next program uses WHILE to make WoW sure the program will only go as long as Answer has the letter y in it CLS DO INPUT Enter the first number A INPUT Enter the second number B PRINT The answer is A B INPUT Would you like to do it again y n Answer LOOP WHILE AnswerS y The condition on the LOOP WHILE line is the same as a condition we might use in an IF THEN In this case we check to see if Answer y and if it does we continue looping If it doesn t we fall out of the loop and our program ends You can add this feature to any program Try adding it to the fortune teller Chapter 14 OR and LEFT That last program works great as long as the user always types in a lowercase y What happens if the user types in yes Since yes is not the same as y to the computer the test for Answer y will fail and the program will end Probably not a good idea We have the same problem if our user enters a capital Y Try a few of these to see what I mean There are several ways to make this program smarter and easier to use for our users We could have it check for a few different ways of saying yes by using OR like this CLS DO INPUT Enter the first number A INPUT Enter the second number B PRINT The answer is A B INPUT
4. DO LOCATE 1 1 PRINT TIMES SLEEP 1 LOOP WHILE INKEYS Not bad at all Now we don t need to teach the user about the Break key We can do the same thing in any of our other programs that need the Break key If the user does not press a key INKEY returns nothing or This next program will sit in a loop getting keys from the keyboard with INKEY and printing them to the screen CLS DO Key S INKEYS IF KeyS lt gt THEN PRINT KeyS END IF LOOP That little program can be used to find the various secret codes used by INKEY to let you know the arrow keys have been pressed This is very useful in game programming where the arrow keys might control a player in a game If you press an arrow key you ll see that a space and a letter are generated Chapter 22 5 String Functions Concatenation Concat uh what It s just a fancy word for putting things together one after another It s much easier done than said When you use the plus sign with strings it doesn t add them up Instead it puts them together AS Hello BS there c AS BS PRINT CS That will print Hello there to the screen LEFTS and RIGHTS LEFT and RIGHTS let you work with parts of strings Try this example AS Ted Felix BS LEFTS AS 3 PRINT B LEFT A 3 means take 3 characters from the left of A Since the 3 characters on the left happen
5. Jack was here or whatever Now run it DO LOOP DO and LOOP will do whatever is between the DO and the LOOP over and over again Give me a Break Ok that s great HOW DO I STOP IT Press the lt Ctrl gt Control key and hold it down while pressing the lt Pause gt key The lt Pause gt key is usually at the top of the keyboard and all the way over to the right This is called pressing the lt Break gt key Don t worry it doesn t really break your program it just stops it and takes you back to QBASIC Maybe it should have been called the brake key On laptop keyboards the break key might be a little harder to figure out Sometimes you have to press the Fn key followed by the key that says break Sometimes it is color coded to help you figure it out You ll know you have it when the program stops and the editor comes back up Neatness Counts Notice that PRINT has two spaces in front of it This is called indenting and it makes the program easier to read You can see the beginning and the end of the DO LOOP more clearly QBASIC doesn t care about indenting only people do It s important to make your programs look nice so other people can read them Learned e File New e DO LOOP e lt Break gt Chapter 5 INPUT So far our programs have only talked to us Let s write one that will listen Get rid of the previous program by clicking on File then New on QBASIC s menu Click on lt No gt when it asks
6. something A T A 1 EFT A 2 T AS 3 This program will print the first character of whatever you enter followed by the first two characters followed by the first three characters Jack J Ja Jac Enter something Jack QBASIC also provides a RIGHTS in case you were curious and it works just like LEFTS Try this INPUT PRINT PRINT PRINT PRINT Enter AS RIGHTS RIGHTS RIGHTS something A AS 1 AS 2 AS 3 Here s an example of what that program will do Jack k ck ack Enter something Jack Chapter 15 COLOR Tired of all this black and white Then the COLOR statement is for you Try this program for size CLS COLOR 2 0 PRINT That s COLOR 3 0 PRINT more COLOR 5 0 PRINT like it Color takes two numbers The first number is the foreground color The second number is the background color For example if you want to print black on white instead of white on black use COLOR 0 7 The colors each have their own number 0 Black 1 Blue 2 Green 3 Cyan 4 Red 5 Magenta 6 Yellow 7 White There are plenty of other colors too Try the numbers from 8 through 15 to see what colors you get Basically if you add 8 to any of the above colors you get brighter versions of the same color Take blue which is 1 and add 8 and you get 9 which is bright blue Blinking Adding 16 to a color number gives you a blinkin
7. Whew That should do it You can close Windows Explorer if you used it get back to your DOS prompt window C WINDOWS gt _ Or C WINDOWS COMMAND gt _ and type qbasic and press the lt Enter gt key QBASIC Books QBASIC by Example Greg M Perry One of the last QBASIC books still in print A really good book that has the right attitude Teaches the right way to program with QBASIC I only took issue with the fact that TYPE is introduced in the random file I O chapter instead of earlier alongside arrays The fact that TYPE is the first step toward object oriented programming makes it very important to introduce it on its own Check it out on Amazon Qbasic by Example Programming Que Absolute Beginner s Guide to QBASIC Greg M Perry Perry s earlier book Out of print but very good You can pick up a cheap used copy on Amazon by clicking here Absolute Beginner s Guide to Qbasic QBASIC for Students Michael Trombetta I have this book but haven t had time to thumb through it and form an opinion It is intended for a High School programming class Microsoft QuickBASIC Bible The Waite Group Comprehensive reference although I don t like the way GOTOs are used and introduced While the authors are cautious to warn against the use of GOTOs they proceed to use them in their SELECT CASE examples No examples are given of the limited situations when GOTOs are appropriate Other than this a very good reference Check
8. could benefit from a Graphical User Interface GUT It s up to you to determine when they are ready If you are an elementary school teacher interested in teaching programming or software development aka software engineering to kids I d suggest starting with Logo at the third or fourth grade level Then move to QBASIC for fourth fifth sixth etc Having to teach a large number of students always presents a challenge as they will each have different abilities Computer programming fits in perfectly with a math curriculum since it helps the students become more aware of numbers and how they work Because of learning to program in BASIC I understood trigonometry by seventh grade I had to because the kinds of programs I was writing required that I understand trig and apply it What could be a better motivation for learning Beyond sixth grade I suspect one could introduce Visual BASIC and continue on up through Java C and into C C at the High School level If anyone has any experience teaching programming at the elementary or middle school level let me know what works for you and I ll add it here At age 11 I learned from a book very similar in style to this one It was the TRS 80 User s Manual and it came with my first Personal Computer the Radio Shack TRS 80 I haven t stopped programming since then I hope this book has the same effect on your kids or maybe even you Please email me with any comments or suggestions to improv
9. it s time to make up some of your own programs QBASIC s help is what you should read through whenever you are curious about everything else QBASIC can do It can do a lot more than what I ve shown you in this book Some of the samples that follow may do things that you haven t seen mentioned in the book See if you can find out what these new things are by looking them up in the help that comes with QBASIC Number Guesser In this game the computer picks a number between 1 and 10 You have to try and guess the number CLS RANDOMIZE TIMER PRINT Welcome to Number Guesser PRINT I m thinking of a number between 1 and 10 Number INT RND 10 1 DO INPUT What is your guess Guess IF Guess Number THEN PRINT Correct EXIT DO ELSE PRINT Try again END IF LOOP Addition Facts Alarm Clock More Samples I have a few more samples on my SupaSoft website Just look for QBASIC Here are a few that you can find there Note If you are typing in these web addresses make sure you use capital letters exactly the way they are shown For example make sure you type SupaSoft not supasoft If you are getting Not Found messages in your web browser this is probably why http www tedfelix com SupaSoft snowflak html Snowflake Snowflake Generator http www tedfelix com SupaSoft strsplt2 html Star Split 2 Starfield simulation http www tedfelix com SupaSoft willtell html Wi
10. 240 100 15 END SUB Notice that after you pressed enter on the first line you were taken to a new screen with just your new SUB in it Now if you go to the SUBs dialog box View SUBs you can see that you have a SUB named DrawCircle and a Main Module named Untitled Now we need to go back to the Main Module Untitled to actually use the new SUB From the menu select View SUBs to get the SUBs dialog box Now double click on Untitled to get back to the Main Module The screen will go blank but don t worry your SUB is still out there Now type this in and run it SCREEN 12 CLS DrawCircle See DrawCircle did what it was supposed to do Let s try adding another SUB See if you can remember the steps on your own Refer back to the previous example if you need help SUB PlayMary PLAY e8 d8 c8 d8 e8 e8 e4 END SUB Now we need to change the Main Module to use our new SUB So go back to the Main Module and change it to look like this SCREEN 12 CLS DrawCircle PlayMary Now run it and you should see the circle and hear the song Dividing programs into smaller pieces like this will help you make sense out of big programs Arguments Sometimes you want to pass numbers or strings to a SUB QBASIC lets you do this Here is a new version of the DrawCircle SUB SUB DrawCircle2 Radius CIRCLE 320 240 Radius 15 END SUB This version lets us pass in the Radius
11. When we do this Radius is called a parameter or argument to our SUB Here s how we would then pass an argument from the Main Module SCREEN 12 CLS DrawCircle DrawCircle2 20 PlayMary We could also do something like this in our Main Module SCREEN 12 CLS FOR I 5 TO 200 STEP 5 DrawCircle2 I NEXT I Changing Arguments If you need to tell the main module something you can change one of the arguments in your SUB and the main module will see the change CLS I 0 AddOne I PRINT I SUB AddOne X X X H 1 END SUB When you run that program it will print the value 1 on the screen This is because the value of I is changed by the AddOne SUB If you only need to return one value a FUNCTION is sometimes a better choice FUNCTIONS are described later Scope What if we had variables in the Main Module and in a SUB that happen to have the same name Would they be the same variable Let s find out Enter this SUB SUB Scope PRINT Scope says X X 23 END SUB And this Main Module X 15 Scope PRINT Main Module says X And run it What happened Scope said 0 because to Scope X was a new variable Main Module said 15 because Scope didn t change Main Module s X it changed it s own X Scope s X and Main Module s X are different variables Variables that you create in a SUB cannot be seen by the Main Module Variables in the Main Module cannot be
12. Would you like to do it again y n Answers LOOP WHILE AnswerS y OR AnswerS Y This version will allow the user to enter y or Y and the program will run again We can get even more clever by using LEFT like this CLS DO INPUT Enter the first number A INPUT Enter the second number B PRINT The answer is A B INPUT Would you like to do it again Answers FirstLetterS LEFTS Answers 1 LOOP WHILE FirstLetterS y OR FirstLetter y This version will let the user enter Yes yes or just about anything that starts with a y because LEFT is used to only look at the first character in their answer You could even enter yep or YEAH and the program will begin again This may seem to make the computer smarter but we know what s really going on To prove the computer really isn t very smart try entering sure or yellow It thinks sure is no and yellow is yes LEFTS LEFT can be used to take a certain number of letters from the left side of a string variable As an example if we have AS TEST Then LEFT A 2 will give us TE LEFT A 3 will give us TES The first parameter you pass to LEFT is the string you want to work with The second parameter you pass to LEFT is the number of characters letters you want Let s try a program that uses LEFT in a different way INPUT PRINT PRINT PRINT PRINT Enter AS EFI EF
13. command PRINT PRINT prints things to the screen Don t forget to put what you want to say in double quotation marks Press any key to continue At the bottom of the screen you will see a message Press any key to continue Press lt Enter gt to get back to QBASIC This is QBASIC s way of giving you enough time to see what your program did As a cool shortcut use for PRINT Try it Press lt Enter gt to start typing on a new line Now type this Programming is fun and press lt Enter gt again Isn t that nice The becomes the word PRINT That should save us a lot of typing in the long run You can try running the program again remember Click on Run then Start on the menu You should see something like this C WINDOWS gt qbasic Welcome to QBASIC Your wish is my command Welcome to QBASIC Your wish is my command Programming is fun Learned QBASIC screen Editing Keys PRINT Run Start 9 Chapter 3 CLS It was probably a bit hard to find your messages on the screen with that last program Wouldn t it be nice to be able to clear all that stuff off the screen CLS which stands for CLear Screen is just the ticket You will need to put CLS at the very top of your program to clear the screen before you print anything Inserting a new line at the top To make CLS the first line of your program follow these steps e Press the lt Home gt key to get to the beginning of the current lin
14. file on the hard disk called testfile txt You can use Notepad to find it and make sure your name is there You might need to figure out where QBASIC put the file That can be a little tricky If you exit QBASIC and from the DOS prompt enter this type testfile txt You should see your name or whatever you entered The type command at the DOS prompt copies the contents of a file to the screen You could also try this notepad testfile txt That should bring up notepad with your file When you are working with files it is a good idea to know how to bring them up in notepad This way you can look at them to see if they contain what you expected OPEN WRITE and CLOSE There are three statements OPEN WRITE and CLOSE that are needed to write information to a file The OPEN statement tells QBASIC three things 1 The name of the file testfile txt 2 Whether we want to write to the file OUTPUT or read from the file INPUT 3 The file number 1 in this example Once the file is opened we will use the file number to let QBASIC know which file we want to write to You could have many files open at the same time so the file number lets QBASIC know which file you want to work with The WRITE statement tells QBASIC which file we want to write to 1 and what we want to write Name It is very much like a PRINT statement but instead of sending the information to the screen WRITE sends the information to a file Finally
15. http www ethanwiner com Ethan Winer s site His book BASIC Techniques and Utilities is available for download here e http piptol qbasicnews com webring goring php action all The QBASIC web ring lots of other interesting QBASIC sites e http deger republika pl QBASIC info in Polish Here you ll also find a Polish translation of this book at http deger republika pl TedFelix OBforKids htm e http www libertybasic com Another flavor of BASIC for windows I don t recommend LibertyBASIC because its graphics support is difficult to use It is very important that a programming language have an easy way for kids to play with graphics e http www qwerty com basic htm e http www conklinsystems com retro trsman shtml Takes me back I managed to land a paper copy of the old TRS 80 manual and you can download a PDF if you are interested See above Copyright 2007 Ted Felix All Rights Reserved May be copied or translated freely for non commercial use
16. if you want to save the old program now Try this CLS INPUT Enter your name Name PRINT Hello Name How are you today Don t forget the comma between Enter your name and Name Run it When it asks type your name then press the lt Enter gt key What s in a Name Name is called a variable To be variable means that things can change Try running the program again but this time type in a friend s name don t forget the lt Enter gt key Sure enough the message changes INPUT INPUT Name takes what you type at the keyboard and puts it into the Name variable PRINT Name prints out what is in the Name variable Variables Variables hold letters and numbers The dollar sign means this variable can hold letters These are called string variables Variables without a dollar sign can only hold numbers We ll be seeing them soon You can call your variables anything you want Try going back through this program and changing every Name to Fred What happens when you run it Another way to think of a variable is to imagine a small bucket with a name on it Put Name on it This is the bucket s variable s name Now ae take a piece of paper and write your name on it and drop it into the imaginary bucket Now the variable Name has your name in it Computer Named variables can only hold one piece of paper one value at a time PRINT and Variables When you want to PRINT what s i
17. it out on Amazon Waite Group s Microsoft Quickbasic Bible More Books Click here for QBASIC books at Amazon Here are some titles I ve found at Amazon I don t know anything about these since I haven t reviewed them QBasic for Beginners Fenton et al Qbasic Susan K Baumann et al Apparently this one was used in high schools to teach QBASIC QBASIC Programming for Dummies Douglas A Hergert The famous Dummies series Reviewers at Amazon indicate that this book isn t as gentle as it should be Programming With Qbasic Prisma Be an Expert Series Computerbooks for Young People ISBN 1 853 65346 2 Special Order from www amazon com Building with BASIC A Programming Kit for Kids Gayle Arthur Alpha Books 1992 ISBN 0 672 30057 5 Uses QBASIC Out of Print QBASIC Using Subprograms 2nd ed James S Quasney Quickbasic and QBASIC Using Modular Structure Julia Case Bradley There are two editions one from 10 1993 and one from 11 1995 called the Alternate Edition that includes some added Visual BASIC info My old TRS 80 books that I learned from TRS 80 Micro Computer System User s Manual for Level 1 Dr David A Lien This is the book I started with back in 1979 A PDF copy is available at http www trs 80 com TRS 80 Level II Dr David A Lien Other Websites e Google s list of QBASIC tutorials e http www network54 com Forum 13959 QBASIC Forum talk to other folks who use QBASIC e
18. ll need to have a program up on the screen for this to work properly Go back to the previous chapter and type in the example if you need to get something up on the screen Click on File on QBASIC s menu then Save The Save dialog will appear on the screen Notice that the cursor is in a box field called File Name Type this a testsave Be careful with that backslash It isn t the same as the front slash which is on the same key as the question mark QBASIC is very picky about this Press the lt Enter gt key What happened Did you hear something Where d the Save dialog go Hmmmm ok hopefully that worked How can we check Let s try loading the program back into QBASIC Wait it s already there Ok then let s clear it out and try to get it back from the floppy Remember how to get rid of a program Hint File then New on the menu Loading From Floppy Let s do it Click on File then Open on QBASIC s menu Now you will see the Open dialog Type this a and press the lt Enter gt key Now you should see TESTSAVE BAS in the box called Files Two clicks oughta do it Double click on TESTSAVE BAS and the program is back from the floppy Saving To Hard Disk The hard disk is the most convenient place to save programs Since it is always in the computer your programs are always there for you to load when you need them Neatness Counts Again Hard Disks usually have a lot more inf
19. our variables We can fill in variables on our own inside our programs too Like this CLS A 1 B 2 AS Hello PRINT A PRINT B PRINT AS A 1 places the value 1 in the variable A B 2 places the value 2 in the variable B A Hello places the string Hello in the variable A You get the picture Then the program prints them out to prove to you that they are there See if you can figure out what this rather clever program will do Then type it in and run it to see if you were right CLS Count 1 DO PRINT Count Count Count 1 LOOP Did you get it right Did the output go by way too fast You ll have to press Break to stop it Then take a closer look and see if you can see what s going on That program is what is called a counter It counts 1 2 3 4 until it is stopped Chapter 11 Random Numbers Random numbers are numbers that you can t predict Flipping a coin or rolling dice will give you a random number Random numbers are very important in games and in some kinds of Math Computers can generate random numbers pretty well QBASIC s RND function provides random numbers that we can use RND RND is a special function that gives us a random number between 0 and 1 We can use this in games to make things interesting RND is perfect for rolling dice or flipping a coin First let s see RND in action CLS PRINT RND PRINT RND This program will print RND twice Notice that you ll get two numbers t
20. s an improvement to a previous program CLS INPUT Enter your name Name IF LCASES Name mike THEN PRINT Go Away BE iS BE PRINT Hello Name How are you today END IF In this new version the user can type mike Mike or even MIKE and the name will be recognized STRINGS and SPACES Let s say you need to print 20 stars on the screen in a line You could do it like this PRINT WAKKKKKKKKKKKKKKAKKKKKAKAEAN But there has got to be a better way How about with a FOR loop FOR I 1 to 20 PRINT Tang NEXT I PRINT That works well but QBASIC provides an even easier way to do this with STRINGS PRINT STRINGS 20 The first argument to STRING is the number of times you want a character repeated The second argument is the character you want to repeat So STRING 20 means give me 20 stars If you want to print a lot of spaces you could do it with STRING PRINT A STRINGS 20 B Or you can use SPACE PRINT A SPACES 20 B FOR loops always make things interesting FOR I 0 to 20 PRINT SPACES I QBASIC NEXT I LENO LEN gives you the length of a string Try this AS Hello PRINT LEN AS As expected that should print the number 5 since the word Hello has 5 characters LENO is handy in FOR loops when you aren t sure how long the string is and you don t feel like counting it yourself
21. s more than one way to do triplets 8th note triplets can also be called 12th notes like this LAY lt d1l2d12d12g2 gt d2 LAY cl2 lt b12al12 gt g2d4 LAY cl2 lt b12al12 gt g2d4 P P PLAY c12 lt b12 gt c12 lt a2 gt Using this technique 16th note triplets are 24th notes etc You just multiply the note value by 1 5 instead of changing the tempo Each of these techniques has its advantages and disadvantages The tempo changing technique uses more space but the notes retain their values The 12th note technique is more compact but not as easy to understand Which one you use is up to you Just make sure the next person to read your code understands what you are doing Comments are a good idea Chapter 18 LOCATE LOCATE allows you to print in a specific place on the screen CLS OCATE 5 10 PRINT Here OCATE 20 70 PRINT There The two numbers after LOCATE are the coordinates where the print will be Just like coordinates in math class these numbers give the row and the column The first number in LOCATE is the row or how far down the screen the print will start The second number is the column or how far over the print will start Let s use some random numbers COLOR and LOCATE to make a more interesting version of our first looping program CLS DO Row INT RND 23 1 Column INT RND 79 1 LOCATE Row Column Colorl INT RND 15 1 COLOR Colorl 0 PRINT Ted was here
22. such option so we have to use PAINT SCREEN 12 CLS CIRCLE 320 240 100 15 PAINT 320 240 15 15 PAINT fills an area with a color It stops painting when it runs into a certain color on the screen The coordinate 320 240 tells PAINT where to start filling in and the first 15 tells PAINT to use bright white as the paint color The second 15 tells PAINT to stop painting when it runs into anything that is bright white Circle Art Concentric circles are very easy to draw SCREEN 12 CLS FOR I 5 TO 200 STEP 5 CIRCLE 320 240 I 15 NEXT I With CIRCLE PAINT and some random numbers we can make some interesting pictures SCREEN 12 CLS FOR I 1 TO 50 X INT RND 640 Y INT RND 480 R INT RND 100 Colorl INT RND 16 CIRCLE X Y R Colorl PAINT X Y Colorl Colorl NEXT I Chapter 22 INKEY Up to now we ve been using INPUT to get things from the keyboard The problem with INPUT is that our program stops until the user presses the enter key Wouldn t it be nice to keep the program running and still be able to get input from the keyboard INKEY will let you do this Using INKEY is very important if you want to make real time game programs Let s fix the clock program to let the user press any key to stop the program This way the user doesn t have to know about the Break key CLS LOCATE 3 1 PRINT Press any key to exit
23. the previous chapter and type in the example if you need to get something up on the screen Click on File on QBASIC s menu then Save The Save dialog will appear on the screen The cursor is in a box field called File Name Type this c TedsPrgs Once again watch the backslash Change TedsPrgs to whatever you named your directory Press the lt Enter gt key Now you will see a list of programs in that directory Since you haven t saved anything yet there shouldn t be any programs there Go ahead and type this testsave and press the lt Enter gt key Hmmm no sound at all that time Hard disks are much more quiet than floppies So let s make sure it worked properly First get rid of what s on the screen with a File then a New Loading From Hard Disk This is also very similar to the way we loaded a program from floppy Click on File then Open on QBASIC s menu This will bring up the Open dialog Type this c TedsPrgs Like before watch the backslash and change TedsPrgs to whatever your folder was called Now you should see TESTSAVE BAS in the Files box Double click on TESTSAVE BAS to load it That wasn t too bad was it Once you figure out whether you want to save to floppy or hard disk you only need to remember one way to save and load Learned e Saving to floppy e Loading from floppy e Creating a folder e Saving to hard disk e Loading from hard disk Chapter
24. to be Ted this program prints Ted as expected Try changing the number to 2 or 5 and see what happens Once you understand LEFT RIGHTS is easy Let s try it AS QBASIC is cool BS RIGHTS AS 4 PRINT B RIGHT A 4 means take 4 characters from the right of A This gives us cool MIDS LEFT gives us something from the left side of a string RIGHTS gives us something from the right side of the string MID gives us something from the middle of a string Try this AS one two three BS MIDS AS 5 3 PRINT B MID A 5 3 means take 3 characters from the middle of A starting at the fifth character This gives us the word in the middle two You can also use MID to change a portion of what is in a string variable Try this AS cabinet PRINT A MIDS AS 4 2 ar PRINT A Here we replaced the in in cabinet with ar This gives us a completely different word This would be a pretty sneaky way to hide something like a password in a program Someone who didn t know how to program in QBASIC might not be able to figure it out LCASES and UCASES If you need to convert a string to all uppercase or all lowercase UCASE and LCASE are exactly what you need AS Fly Away With Me PRINT AS PRINT UCASES A PRINT LCASES AS You can use UCASE and LCASE to do case insensitive tests In other words upper and lower case are ignored Here
25. your c windows command directory Click on the Start button then Programs then Windows Explorer On the left you will see a list of the drives on your computer Look for the CD ROM drive it has a little picture of a CD and it should say Windows95 next to it Click on the picture In the right column you will see a list of directories on the CD Finding QBASIC Double Click on Other then double click on Oldmsdos Now you will see a list of files Go through the list until you find the two files with the name Qbasic One is QBASIC itself and the other is a help file Selecting the two QBASIC files We want to copy these two files to the c windows command directory Click on the first Qbasic file to turn it blue This means it is selected We also need the other Qbasic file Press and hold the lt Ctrl gt key while you click on the other Qbasic file They should both be blue now This means they are both selected Copying To The Clipboard Press the lt Ctrl gt key and hold it down while pressing the C key This will copy the files to the clipboard Destination C Windows Command Now click on Tools on the Windows Explorer menu then click on Go To Type this c windows command and press the lt Enter gt key Pasting From The Clipboard Now press the lt Ctrl gt key and hold it down while pressing the V key This will paste the qbasic files from the clipboard and into the c windows command directory Finished
26. 10 O MWAA AO BWNE A A A A A A A A A i FOR I 0 TO 8 PRINT A T NEXT I To save space and typing QBASIC provides the DATA and READ statements You can place a list of data values in a DATA statement and read them into an array using READ The following program will do exactly what the previous program does DATA 10 24 31 15 67 34 87 92 14 FOR I 0 TO 8 I READ A NEXT I FOR I 0 TO 8 PRINT A I NEXT I QBASIC skips the DATA statements in the code It only pays attention to them when it finds a READ statement Each time a READ happens QBASIC takes a value from the DATA statement and places it in the variable in the READ statement RESTORE RESTORE tells QBASIC which DATA statement to start READing from You might need to load several different arrays in your program RESTORE lets you organize the DATA statements any way you want Names DATA Fred Joe Jack Sue Values DATA 10 24 31 15 67 34 87 92 14 Start with the DATA statement after Values RESTORE Values FOR I 0 TO 8 READ A T NEXT I Start with the DATA statement after Names RESTORE Names FOR I 0 TO 8 READ N I NEXT I RESTORE tells QBASIC to start reading at the next DATA statement after a label A label is a name like Names or Values Notice that when we make a new label we use a colon but when we use the label in the RESTORE stat
27. 2 AS FriendType Fill the database with names and numbers Friends 0 FullName Joe Blow Friends 0 PhoneNumber T 310 555 1212 Friends 1 FullName Jack Sprat Friends 1 PhoneNumber V1 340 555 6545 Friends 2 FullName Carol Christmas Friends 2 PhoneNumber 1 350 555 2421 Print out the entire database FOR I 0 TO 2 PRINT Friends I FullName Friends I1 PhoneNumber NEXT I Chapter 25 5 Type Conversion STRS Q and VALO Up to now we ve been using string variables to hold strings and number variables to hold numbers What if we really need to do some math with numbers that are in a string variable Or maybe we need to get some numbers into a string variable somehow QBASIC provides the STR and VALO functions to help us out STR will let us convert from a number to a string Like this A 25 A can only hold numbers PRINT A BS STRS A Convert A to a string store in BS PRINT BS VAL will let us convert from a string to a number Like this AS 25 Can t do any math with a string variable PRINT A B VAL AS Convert AS to a number store in B PRINT B Converting Numbers Need to cover CINT FIX INTO CDBL CSNG CLNG Chapter 25 75 PRINT USING Chapter 25 9 DATA and READ Loading an array with a lot of values can get pretty boring Load up the array
28. 9 SELECT CASE IF THEN ELSE is fine if you only have two things you want to check What if you have 5 or 6 friends that might use your computer and you want the computer to say something different to each of them Try this CLS INPUT Enter your name Name SELECT CASE Name CASE Ted PRINT Greetings oh powerful master CASE Mike PRINT Go away CASE ELS PRINT END SELECT Hello NameS How are you Whew that was a big one Fortunately we learned how to save in Chapter 8 Save it if you want before running it Feel free to change Ted and Mike to Laura and Robin or whoever SELECT CASE SELECT CASE first checks Name for the value Ted If it finds it it does the PRINT after the CASE Ted When the PRINT is done it skips over the rest of the CASEs It keeps checking against each CASE until it gets to CASE ELSE If it hasn t found anything it will do whatever is after the CASE ELSE Just In CASE SELECT CASE can also be used with numbers as well as strings Here s a quick example CLS INPUT Enter a number Number SELECT CASE Number CASE 1234 PRINT Thank you for entering the secret number 1234 CASE 22 PRINT Well 22 is an interesting number CASE ELSE PRINT You must not know the secret number END SELECT Learned e SELECT CASE Chapter 10 Equals So far we ve only let the user fill in
29. AW to draw a square on the screen in SCREEN 12 graphics mode SCREEN 12 CLS DRAW D100 R100 U100 L100 There are many other SCREEN numbers you can use but 12 is probably the easiest to work with It gives you a lot of space and the color numbers are familiar QBASIC Help explains all the possible values of SCREEN You can always try them and see what happens DRAW DRAW is kind of like the turtle in the programming language Logo With DRAW you can move around the screen and draw lines along the way In the above example we used the following DRAW commands D100 Go down 100 units R100 Go right 100 units U100 Go up 100 units L100 Go left 100 units DRAW can do a lot more than that It is like PLAY It s a small programming language inside of QBASIC Look at QBASIC Help for a complete description of everything it can do Here s a filled in box SCREEN 12 CLS DRAW C15 D100 R100 U100 L100 BF1 P15 15 C15 sets the color to bright white BF1 moves into the square then P15 15 fills it with bright white Finally here s something very Logo like SCREEN 12 CLS FOR I 0 TO 360 STEP 10 DRAW D100 R100 U100 L100 TA STRS T NEXT I TA means to turn to a specific angle STR converts the value in I to a string This lets DRAW turn to the angle in the variable I It s not quite as easy as Logo but it s still pretty impressive LINE QBASIC also lets you draw using a coor
30. Binary I O As opposed to How to do it What is the difference Unformatted unreadable Why is it a good thing Small unreadable to prying eyes fast Sample Write out a few numbers and strings Examine with notepad Read them back in Random I O Up to this point we have been using what is called Sequential I O Sequential means one after another I O stands for Input Output When we write the user s name and the run count to the file we write them one after another This is sequential output When we read the name and run count we read them one after another Name first then run count This is sequential input All together this adds up to Sequential Input and Output or Sequential I O Random I O lets you read and write data to any part of a file in any order you want It is very useful when you have very large files and you don t have enough time or memory to read everything in the file sequentially one after another Random I O lets you jump right to the data you want in a file and read or write it Even in very large and complex programs Random I O is rarely used due to its complexity Imagine if the program has a bug and it writes to the wrong location in the file The file could be destroyed because of this We won t cover Random I O here But if you need it it s in QBASIC Chapter 27 Sample Programs Read the Manual You ve learned a lot If you ve made it through this far and you are still having fun then
31. QBASIC Programming for Kids Introduction You ve probably used computers to play games and to write reports for school It s a lot more fun to create your own games to play on the computer This book will help you get started by using QBASIC QBASIC is a programming language With a programming language you can tell the computer what you want it to do It s a lot like giving someone directions to your house The computer follows each step and does exactly what you tell it By programming the computer you can solve math problems create art or music and even make new games It s all up to you The best way to start with this book is to type in some of the small programs you ll find in each of the chapters You might need to work through Chapter first An adult can help you get up to speed quickly Then change the programs to do what you want them to do Before long you ll be writing your own programs Introduction for Parents and Teachers Kids love computers They also like to create and to have some control over the world around them The computer will do whatever it is told It may not seem that way at times but it is true When I was a kid all we had was the old BASIC It had line numbers and didn t teach good structured programming habits QBASIC is a much better learning tool With the information acquired from this book one can move on to a more advanced QBASIC book if you can find one After becoming proficient in QBASIC one
32. ariable The type character for a string variable is Here are some examples of creating and using string variables x Hello DIM Y AS STRING Y Goodbye PRINT X PRINT Y Integer The integer type handles numbers without decimals Integers may range from 32768 to 32767 Math with integers may be faster than math with single precision variables For programs that have to run very fast using integers might be useful In a DIM statement use INTEGER to create an integer variable The type character for an integer variable is Here are some examples of creating and using integer variables XS 32 DIM Y AS INTEGER Y 55 PRINT X Y Since math with integers is very fast you will commonly see the following line near the beginning of QBASIC programs DEFINT A Z This tells QBASIC to stop assuming that every variable is single precision and instead to assume that all variables are integers This way you don t need to use DIM or the symbol throughout your program to make all your variables integers Long Integer The long integer type handles numbers without decimals Long integers may range from 2147483648 to 2147483647 Math with long integers is usually almost as fast as math with integers For programs that have to run very fast using long integers might be useful In a DIM statement use LONG to create a long integer variable The type character for a long integer variable is amp H
33. as Mike in it If so then it does the PRINT statement after the THEN If Name isn t Mike it does the PRINT statement after the ELSE END IF tells QBASIC that the IF is over Conditions The Name Mike portion of the IF THEN is called the condition With numbers you can also check for greater than and less than CLS INPUT Enter a number Number IF Number lt 100 THEN PRINT Your number was less than 100 B iSE PRINT Your number was greater than or equal to 100 END IF If you want to check for greater than use Number gt 100 Equals works just like before Number 100 Another option is not equal which can be done like this Number lt gt 100 IF THEN is one of the most powerful features of QBASIC Using IF THEN can make your programs very interesting It lets your program make decisions and do something appropriate Learned e IF THEN ELSE Chapter 7 Numbers Computers are very good at math Let s get the computer to do some math for us Here s a simple multiplication calculator CLS INPUT Enter the first number A INPUT Enter the second number B PRINT The answer is A B If you have trouble finding the star or asterisk on the keyboard it is usually above the number 8 Run it and enter two numbers It does an excellent job multiplying for you Variables and Math A and B are variables just like Name U
34. can move on to more powerful languages like Visual Basic Java C and eventually C I would suggest a course of study like this e Logo Teach FORWARD LEFT RIGHT TO REPEAT This shows the basics of programming You can walk kids through all this step by step You ll be surprised how much they ll learn Very young kids can have a lot of fun with Logo Just don t get too deep Make sure it is a lot of fun e QBASIC QBASIC is more like conventional programming languages than Logo so before getting too deep into Logo it s a good idea to switch to QBASIC Kids will be resistant for two reasons no more turtle DRAW is similar see the Graphics chapter and the fact that it s a new language They ll get over it You can teach the basics of QBASIC interactively but at some point you need to turn them loose with this book and let them type in the examples and ask you questions e Visual BASIC All of the skills learned in QBASIC transfer nicely to Visual BASIC Here kids can finally learn to make real windows programs Visual BASIC also includes object oriented programming features that can be introduced to help manage larger programs Visual BASIC versions 4 through 6 have varying levels of Object Oriented support while Visual BASIC 7 0 net is a complete Object Oriented language e Java Introduce C and its cousins gently with Java Object Oriented programming concepts can be introduced here or in Visual BASIC Microsoft s C is a
35. dinate system It s like drawing graphs on graph paper Try this SCREEN 12 CLS LINE 0 0 320 240 15 LINE lets you draw a line between two points The points are specified in x y coordinates You may have seen this when learning about graphs in math class In QBASIC the coordinates are almost the same The only thing that is different is the Y coordinate In QBASIC the Y coordinate is upside down 0 is at the top and bigger numbers go toward the bottom of the screen LINE 0 0 320 240 15 draws a line starting at coordinate 0 0 which is the upper left corner of the screen The line ends at 320 240 which is the center of the screen The last number is the color 15 which is bright white Box By adding a B to the end of a LINE statement you can draw a box Try this SCREEN 12 CLS LINE 0 0 320 240 15 B The first coordinate is the upper left corner while the second coordinate is the lower right Try BF instead of B Interesting CIRCLE QBASIC can also draw circles using the CIRCLE statement SCREEN 12 CLS CIRCLE 320 240 100 15 The coordinate 320 240 tells the computer where to put the center of the circle 100 is the radius or how big the circle will be 15 is the color number bright white again PAINT Notice how that circle was not filled in LINE has a BF option that will let us fill in the boxes it draws CIRCLE has no
36. e e Press the lt Up Arrow gt key once or twice to get the cursor to the top of the program e Press the lt Enter gt key to get a new line e Press the lt Up Arrow gt key once to get the cursor on the new blank line e Type CLS Now your program should look like this CLS PRINT Welcome to QBASIC Your wish is my command PRINT Programming is fun Run it Remember click on Run and then Start in QBASIC s menu You can also run the program by pressing the lt Shift gt key and holding it down while pressing lt F5 gt that s what Shift F5 means on the menu Another handy shortcut That s much better Only your message is on the screen which is the way it should be Learned e CLS ShifttF5 Chapter 4 DO LOOP Let s start a new program To get rid of the old program click on File on QBASIC s menu and you will see the File menu with New Open Save and others Click on New QBASIC will now tell you that your current program is not saved and it will ask if you want to Save it now Let s not save it You can always type it in again Click on lt No gt with the mouse We ll learn how to save programs in Chapter 8 Now you should have a clean blue screen Type in this program DO PRINT Ted was here LOOP Make sure you get the semi colon at the end of the PRINT line and the space between the word here and the last quotation mark You don t need to use my name put yours in there instead
37. e this book My email address ted tedfelix com You can find more information on my Computer Science for Kids page http tedfelix com cs4kids Computer Science for Kids And in case you are looking at a mirror site the latest version of this book is always kept here http tedfelix com qbasic QBASIC Programming for Kids And for all you aspiring programmers in Poland check out Damian s Polish translation at http deger republika pl TedFelix QBforKids htm I hope you and your kids have lots of fun Chapter 1 Getting Started Getting to DOS To run QBASIC we need to get to DOS If you are using Windows 3 1 you ll need to find the Main program group and look for an icon called MS DOS Prompt Double click on it to get the C wINDows gt _ prompt in a black window with white text In Windows 95 click on Start then Programs then MS DOS Prompt Programs US Accessories A Online Services Documents StartUp Settings Internet Explorer 5 Internet Mail Internet News Help Microsoft NetMeeting amp MS DOS Prompt QJ Windows Explorer Find Bun 8 e E ai Shut Down In Windows 98 try the Windows 95 steps above then try the Windows ME steps below It is the same as one of those but I don t have a Windows 98 machine handy to test In Windows ME click on Start then Programs then Accessories then MS DOS Prompt In Windows NT 4 I believe it was called t
38. ement we drop the colon Loading a Database DATA statements are perfect for loading a database Here s a new version of the database example using DATA statements this time DATA Joe Blow 1 310 555 1212 DATA Jack Sprat 1 340 555 6545 DATA Carol Christmas 1 350 555 2421 TYPE FriendType FullName AS STRING 20 PhoneNumber AS STRING 14 END TYPE The database DIM Friends 2 AS FriendType Read in the database from the DATA statements FOR I 0 TO 2 READ Friends I FullName Friends I PhoneNumber NEXT I Print out the entire database FOR I 0 TO 2 PRINT Friends I FullName Friends I1 PhoneNumber NEXT I Chapter 26 Reading and Writing Files Up to now our programs have depended on us the programmer to give them data to work with This wouldn t work very well for a phone book program The user should be the one to fill in the names and phone numbers QBASIC will let us get information from the user with INPUT But when the program ends that information is gone Writing to a file The solution to this problem is to let the user enter their information then the program will store that information in a file on the hard disk QBASIC offers a number of ways to do this Try this INPUT Enter your name Name OPEN testfile txt FOR OUTPUT AS 1 WRITE 1 Names CLOSE 1 When you run that program and enter your name it will place your name in a
39. ere are some examples of creating and using long integer variables X amp 65536 DIM Y AS LONG Y 121072 PRINT X amp Y Double Precision The double precision type handles numbers with decimals You can go up to fifteen digits with a double precision variable Double precision variables are used where very accurate math is needed In a DIM statement use DOUBLE to create a double precision variable The type character for a double precision variable is Here are some examples of creating and using double precision variables X 3 14159265358979 DIM Y AS DOUBLE Y 1 23456789012345 PRINT X Y Arrays An array lets you store a list of things Arrays are very similar to variables but they hold more than one thing Try this N 0 Ted N 1 Jack N 2 JilI N 3 Fred FOR I 0 TO 3 PRINT N I The number inside the parenthesis 1 is called the subscript N 0 is usually pronounced N dollar sub zero although I ve also heard it called N string sub zero Arrays can also store numbers FOR I 0 TO 10 A I I 2 NEXT I FOR I 0 TO 10 PRINT A T NEXT I Arrays are limited to holding only 11 items 0 through 10 If you go over 10 you ll get a Subscript out of range error To make bigger arrays you can use DIM to tell QBASIC how big the array will be DIM A 20 FOR I 0 TO 20 A I I 2 NEXT I FOR I 0 TO 20 PRINT A T NEXT I Arrays a
40. for a while Constants Another way to make your programs easier to understand is to use constants Constants look and act like variables but they cannot be changed Here s a useful program CONST Pi 3 141593 INPUT Enter the radius of a circle Radius PRINT The circumference is 2 Pi Radius PRINT The area is Pi Radius Radius If we didn t use the constant Pi we would have to copy the number 3 141593 two places in the above program Using a constant makes the program easier to read and understand It also keeps us from making mistakes when copying Chapter 24 Sub Procedures SUBs When programs get big you need to break them into smaller pieces that are easier to work with QBASIC calls these pieces sub procedures or SUBs Other programming languages have other names like procedures subroutines or subprograms To work with SUBs in QBASIC we need to look at the SUBs dialog box which shows us a list of our SUBs Select View SUBs from the menu to bring up the SUBs dialog box You can also press the F2 key to get there more quickly In here you can select a SUB to work with or you can select the main module If you are just starting with a clean slate File New you ll see that the main module is called Untitled and there are no SUBs You can define a new SUB in QBASIC simply by typing it in This will jump you to the view of the new SUB Try typing this SUB DrawCircle CIRCLE 320
41. for the next run OPEN register txt FOR OUTPUT AS 1 WRITE 1 Name RunCount CLOSE 1 This END prevents us from running the error handler at the end of the program It causes the program to stop just like pressing the Break key END QBASIC will jump here if an error occurs rrorHandler We have to move the error code into a variable or we won t s it because ERR is set to zero after the handler is done ErrorCode ERR RESUME NEXT Handling File Errors ON ERROR GOTO ErrorHandler tells QBASIC that if there is a problem the program should immediately jump to ErrorHandler which you will see near the end of the program There we can get the error code which is in a QBASIC variable called ERR and copy it to our own variable ErrorCode If we don t do this we will lose the error code stored in ERR RESUME NEXT tells QBASIC to continue from where the error occurred I try very hard to avoid using GOTO in my programs Programs that use GOTO can be very hard to understand Unfortunately in this case QBASIC leaves us with no alternative We have to use a GOTO So I ve tried to come up with the simplest solution that keeps the code from being too hard to follow With this little error handler in place we can simply assume that ErrorCode will contain the error number when something goes wrong Just don t forget to reset it or you will be looking at old errors
42. g QBASIC Editor If you ve used your computer to do school work or write a report you ll notice that most of the editing keys lt Backspace gt lt Delete gt lt Insert gt work just the way they always do In case you haven t used these keys before here s a list e lt Backspace gt Removes the character to the left of the cursor e lt Delete gt Removes the character at the cursor e lt Left Arrow gt Moves the cursor left e lt Right Arrow gt Moves the cursor right e lt Up Arrow gt Moves the cursor up e lt Down Arrow gt Moves the cursor down e lt Home gt Moves the cursor to the start of a line e lt End gt Moves the cursor to the end of a line Your First Program With the blinking cursor _ at the top left corner of the screen type this PRINT Welcome to QBASIC Your wish is my command Make sure it looks exactly like that The quotation marks are very important If you make any mistakes use the lt Backspace gt key to correct them MS DOS Prompt QBASIC Running Your Program That s great but what does it do You have to run it to find out Look for the word Run on QBASIC s menu at the top of the screen Click on it Now you will see a menu with a list of selections Start Restart and Continue Click on Start to run your program You may have to look around on the screen a bit but you should find your message C WINDOWS gt qbasic Welcome to QBASIC Your wish is my
43. g blank blue screen MS DOS Prompt OBASIH Now we re ready to program Getting Out If you need to leave QBASIC you can click on File on QBASIC s menu and then Exit to get back to DOS xr lela es A Edit View Search Run Debug Opt SSS Unt it led ii rint At the c wINDows gt prompt type exit and then press the lt Enter gt key to get rid of the DOS window Microsoft R gt Windows 95 CG gt Copyright Microsoft Corp 1981 1996 C 2 WINDOWS gt qbas ic C WINDOWS gt exit_ Chapter 2 PRINT Follow Along I m assuming you will be following along with QBASIC in front of you This won t be much fun if you aren t So power up the computer and get QBASIC s blue screen up in front of you Go ahead and press the lt Esc gt key to clear this dialog box when it asks you QBASIC s Screen Before we start let s take a look at QBASIC s screen At the top is QBASIC s menu The menu has the following items File Edit View Search Run Debug Options and Help Clicking on any of these with the mouse will show more selections Just under the menu is the word Untitled This means we haven t given the current program a name This will change when we learn to save programs The big blue area with the blinking cursor _ is where we can enter our programs These are the most important areas to know for right now We will learn more about the rest of QBASIC s screen as we go alon
44. g version This doesn t work in a DOS window though Press lt ALT gt lt ENTER to switch to full screen mode which will show the blinking Try this program CLS COLOR 28 0 PRINT WARNING COLOR 15 0 PRINT Programming can be too much fun Color can be used in many ways to make your programs more interesting Chapter 16 FOR NEXT A New Counter FOR NEXT is a loop like DO LOOP but a FOR NEXT loop has its own counter built in Try this CLS FOR I 1 TO 10 PRINT I NEXT I Much better than our last counter This one stops on its own after counting to 10 A Color Chart Here s a color chart program using a FOR NEXT loop CLS FOR I 1 TO 15 COLOR I 0 PRINT 1 COLOR NEXT I STEP FOR NEXT can also do step counting Try this CLS FOR I 2 TO 20 STEP 2 PRINT I NEXT I That will count by 2 s from 2 to 20 STEP tells QBASIC what to count by Try changing it to count by 10 s from 10 to 100 FOR NEXT can also count backwards if you use a negative STEP value CLS FOR I 10 TO 1 STEP 1 PRINT I SLEEP 1 NEXT I PRINT BLAST OFF SLEEP 1 tells QBASIC to wait for one second then continue Chapter 17 Sound If you just need a beep in your program you can use BEEP CLS INPUT Press Enter to hear a beep AS BEEP SOUND lets you play a beep and tell it how high or low the beep will be and how long i
45. hat appear to be unpredictable and random But try running the program again You ll get the same random numbers This means your games would always be the same each time the user runs them Fortunately there s a way to fix this RANDOMIZE TIMER Using RANDOMIZE TIMER will make sure the random numbers you get are different each time you run Try this CLS RANDOMIZE TIMER PRINT RND PRINT RND Useful Random Numbers Random numbers between 0 and aren t really very useful What you will need for a game might be a random number between 1 and 6 like when you roll dice To get something more useful we ll use math Fortunately computers are very good at math There are two problems we must solve to get the results we want First the range of random numbers has to be expanded from 0 through to 1 through 6 That s easily done like this CLS RANDOMIZE TIMER PRINT RND 6 1 PRINT RND 6 1 By multiplying by 6 we increase the range to 0 through 5 By adding 1 we shift the range up to 1 through 6 However there s still a problem All that decimal stuff QBASIC s INT function can be used to convert a decimal number to an integer a number without a decimal CLS RANDOMIZE TIMER PRINT INT RND 6 1 PRINT INT RND 6 1 Roll the Dice Here s a program that rolls two dice and prints the value of each The variables Diel and Die2 are used to hold the values of each d
46. he Command Prompt Try the steps described for Windows 2000 below In Windows 2000 it is called the Command Prompt and you can find it by clicking on Start then Programs then Accessories then Command Prompt In Windows XP it is called the Command Prompt and you can get to it by clicking on Start then All Programs then Accessories then Command Prompt You will get the black window with the c wINDows gt _ prompt MS DOS Prompt Now you re ready for the next step Starting QBASIC QBASIC may not be on your computer Don t be alarmed Appendix A shows you how to get it there At the c WINDows gt _ prompt try typing qbasic and press the lt Enter gt key ft lt R gt Windows 95 opyright Microsoft Corp 1981 1996 C WINDOWS gt qbas ic_ MS DOS Prompt OBASH Cesi SD File Fate Uieu Search Bun ikuy Out T co ighe C Misrosoft Corporation 1997 1992 sv All rights poserved Press Ente be Survival Guide lt Prose ESC to clear this dialog box gt If instead you got something about a Bad command or file name Microsoft R gt Windows 95 CC gt Copyright Microsoft Corp 1981 1996 C WINDOWS gt qbas ic Bad command or file name C WINDOWS gt _ you need to check out Appendix A to get QBASIC installed on your machine Don t worry we ll wait right here for you Survival Guide We won t be using the survival guide right now so press the lt Esc gt escape key to get the bi
47. ie before printing In a real game Diel and Die2 would be used in some clever way to change the outcome of the game CLS RANDOMIZE TIMER INPUT Press ENTER to roll dice AS PRINT Diel INT RND 6 1 Die2 INT RND 6 1 PRINT Die 1 Diel PRINT Die 2 Die2 PRINT By Itself Note that in the last program there was a PRINT on a line by itself Did you see what it did It simply printed a blank line on the screen This can be useful for making the output from your program look nicer Chapter 12 The Fortune Teller Here s a fun program that uses most of what we ve learned so far to make a Magic 8 Ball CLS RANDOMIZE TIMER PRINT I am the magical Fortune Teller INPUT Think of a question and press enter for your answer AS PRINT Answer INT RND 5 1 SELECT CASE Answer CASE 1 PRINT Yes definitely CASE 2 PRINT Ask again later CASE 3 PRINT No way CASE 4 PRINT It is certain CASE 5 PRINT Yes END SELECT As always go ahead and customize it Change No way to You bet to get a Fortune Teller that never says No Adding CASEs Go ahead and try adding a new fortune You ll need to change Answer INT RND 5 1 to Answer INT RND 6 1 since there will be 6 fortunes now Then you will need to adda case 6 and a PRINT to print the new fortune Chapter 13 DO WHILE
48. inds the string it will tell you where it is Try this AS Hello everyone PRINT INSTR AS every That program prints 7 because every is found at the 7th position in Hello everyone If the string isn t found INSTR returns zero INSTRQ can come in very handy when you want to break a string into pieces AS two pieces SpacePos INSTR AS PRINT LEFTS AS SpacePos PRINT RIGHTS AS LEN AS SpacePos Chapter 23 Comments and Constants Most programming languages allow you to add notes to your programs that are ignored by the computer This lets you explain what you ve done to someone else who might read your program later In QBASIC we use the apostrophe to begin a comment Here s an example A program to draw boxes all over the screen This is a comment QBASIC will ignore it SCREEN 12 CLS Draw 50 boxes FOR I 1 TO 50 Pick the location of the box X1 INT RND 640 Y1 INT RND 480 X2 INT RND 640 Y2 INT RND 480 Pick the color for the box Colorl INT RND 16 Draw the box LINE X1 Y1 X2 Y2 Colorl BF NEXT I The computer will ignore all those comment lines but us humans can read them and remember how a program works Good programmers use comments to help others understand what they have done Comments can also help us remember what we did when we come back to a program after working on something else
49. lliam Tell Pretend to be William Tell and try to shoot the arrow off your victim s head http www tedfelix com SupaSoft capture html Capture Try to trap two robots in a maze of blocks http www tedfelix com SupaSoft My freeware site Look for QBASIC in the program descriptions to find the QBASIC samples Appendix A Finding and Installing QBASIC If you see a message like Bad command or file name then you need to get QBASIC on your machine MicrosofttK Windows 95 CCoCopyright Microsoft Corp 1981 1996 C WINDOWS gt qbas ic Bad command or file name C2 WINDOWS gt _ Unfortunately this isn t the easiest thing in the world to do You might want to get someone to walk through this with you On the Internet There are several places on the internet where you can get a copy of qbasic Usually the file is called qbasic zip Here are some places I ve found it e http www svatopluk com qbtutor tut1 htm QBASIC tutorial at King Svatopluk s Court There are probably a lot of other places to find it too Using a search engine like www google com and searching for qbasic zip usually does a good job If you end up looking for qbasic this way be sure to get the version 1 1 interpreter That is the version of qbasic I used to write this book It is the most easy to use and least complicated Once you are used to 1 1 you can try and find 4 5 which has some very nice features Once you have qbasic zip
50. n a variable leave off the double quotation marks This program will show you how this works CLS INPUT Enter your name NameS PRINT Names PRINT Name The first PRINT statement prints Name on the screen The second PRINT statement prints whatever name you entered Learned e INPUT e Variables Chapter 6 IF THEN Let s make that last program a little smarter I want to be able to identify intruders playing with my programs Wouldn t it be great if the computer could recognize someone s name and print a special message for them How about this CLS INPUT Enter your name Name IF NameS Mike THEN PRINT Go Away B iS E PRINT Hello Name How are you today END IF You can change the Name Mike to Name Joe or whoever you want to go away like a brother or sister Run the program and type in your name hopefully it isn t Mike You should see the same old message as before Now run it again and try entering Mike or Joe or whatever you changed it to Mike Is Not The Same As mike If it didn t tell the right person to go away make sure you typed the name correctly In QBASIC Mike is not the same as mike so if you don t type the first letter in upper case the program won t work Make sure you enter the name exactly the way you put it in the program IF THEN The IF THEN ELSE END IF statement in this program checks to see if Name h
51. nlike Name A and B do not have a dollar sign after their names This is because they are only holding numbers not letters Star A B means A times B QBASIC doesn t use X for multiplication because you might want to have a variable called X What else Try changing the A B to A B for subtraction A B will do addition and A B will do division Why for division Because there s no division sign key on the keyboard At least I haven t found one Expressions A B A B A B and A B are called mathematical expressions or simply expressions Learned e Variables with numbers e INPUT with numbers e Multiplication Division Addition Subtraction e Expressions Chapter 8 Saving Before we get into some fairly big programs let s look at how to save our masterpieces Location Is Everything The first thing we need to think about is where we are going to save our programs The two main places we can save things are the hard disk and onto a floppy disk Let s look at both places Saving To Floppy Using a floppy is a good idea if you don t want other people looking at your programs The floppy can be removed from the computer and kept in a safe place Floppies are also good when you want to move programs from one computer to another Let s try it Find a blank floppy and place it into the computer s floppy drive The floppy can have stuff on it as long as there is some free space left You
52. nother alternative to Java The big draw here is being able to develop cool applets to run on the web e C Since C is probably the most marketable language of all it has to be learned if you are serious about a programming career The big plus for C is raw speed Even compiled BASIC programs can t compete When your kid starts really pushing the limits of BASIC keep mentioning C as being even better That will make them very curious e C A better C and object oriented programming concepts make C a must learn Not to mention the fact that C programmers are hard to find and are very well paid The raw speed of C and the object oriented power of Java all wrapped up into one e Assembler At some point the truth about what s really going on under the covers must be told Assembler can be introduced at any time throughout the learning process to explain how the computer really works Keep bringing it up as being even faster than C Obviously you ll have to determine when your child is ready to move from one language to another My rule is that QBASIC should be introduced at a point where children can learn on their own from this book 10 or 11 years old Then let them go and master it by themselves This gives them a huge feeling of accomplishment As you see them reaching the limits of what can be done introduce them to other languages The jump from QBASIC to Visual BASIC should be made when it is obvious that your child s programs
53. ormation on them than a floppy Because of this you need to be concerned about keeping things neat You ll never be able to find what you need otherwise The best way to organize your collection of programs is to put them into a subdirectory or folder on the hard disk Making Your Own Subdirectory Let s make a folder on the hard disk for our programs In Windows 95 we will need to use Windows Explorer In Windows 3 1 we will use File Manager First the Windows 95 way Making a Folder With Windows 95 Click on the Start button then Programs then Windows Explorer Now click on File then New gt then Folder on the Windows Explorer menu Notice the words New Folder on the right hand side of Windows Explorer Go ahead and type in a name for the new folder but keep it short QBASIC is an older program that can t handle names bigger than 8 letters or numbers I called mine TedsPrgs meaning Ted s Programs Call yours whatever you want but no more than 8 characters or it will look real funny to QBASIC Press the lt Enter gt key to create the folder Good that s done We won t need to do that again unless you d like to make another directory at a later date Go ahead and close Windows Explorer and get back to QBASIC Making a Folder With Windows 3 1 Saving In The Directory Saving to the hard disk is only a little different from saving to a floppy You ll need to have a program up on the screen to save Go back to
54. re perfect for programs that need to keep a list of things You could use arrays to make a phone book program or a program that keeps track of the people in your class at school TYPE Sometimes you ll want to put a bunch of different kinds of variables together because all together they describe something QBASIC s TYPE statement lets you create your own collections of variables Here s an example TYPE FriendType FullName AS STRING 20 PhoneNumber AS STRING 14 END TYPE DIM Friend AS FriendType Friend FullName Joe Blow Friend PhoneNumber 1 310 555 1212 PRINT Friend FullName Friend PhoneNumber TYPE makes our new type or collection of variables DIM makes a new variable of that type When we work with types we use the variable name followed by a dot followed by the name of the variable in the TYPE Since TYPE lets you use a single variable to represent a collection of variables you can use TYPE to pass many parameters to a SUB at once This may be a good way to avoid using SHARED too much in a SUB In QBASIC a TYPE can hold any of the built in types A TYPE can also hold another TYPE However a TYPE cannot hold an array Visual BASIC allows that but not QBASIC A Database Using arrays and TYPEs together allows you to create what is known as a database Try this TYPE FriendType FullName AS STRING 20 PhoneNumber AS STRING 14 END TYPE The database DIM Friends
55. re programming languages that provide Object Oriented programming features and are fairly easy to learn STATIC Notice that each time you call a SUB its variables are lost after the SUB is over Here s an example SUB Counter C Grd PRINT C END SUB CLS Counter Counter Counter Not a very good counter since it always prints 1 We can use STATIC to tell QBASIC that we don t want C to go away after the SUB is over Then we will get the behavior we expect Change the Counter SUB like this SUB Counter STATIC C C C 1 PRINT C END SUB That s much better Object Oriented programming languages offer many ways to avoid the use of STATIC variables If you find yourself making lots of STATIC variables it is probably time to learn an Object Oriented programming language Functions Functions are just like SUBs but they return a value Here s an example FUNCTION Add X Y Add X Y END FUNCTION And here s a Main Module to go with it PRINT Add 3 4 Well I DECLARE As you ve been entering the example programs in this chapter you may have noticed that the QBASIC editor adds DECLARE statements to the programs Why does it do this The DECLARE statement is a warning to QBASIC to let it know that there are SUBs or FUNCTIONS in this program Without this warning QBASIC would have no idea what we mean when we call a SUB or FUNCTION It would think it had found a syntax error and the program would s
56. seen by a SUB If you need to share variables you can pass them as arguments to the SUB Global Data It is possible to make variables in the Main Module available to SUBs without passing them as arguments Add a SHARED X to the Scope SUB like this SUB Scope SHARED X PRINT Scope says X X 23 END SUB Now when you run it you ll see that the Scope SUB can now see the Main Module s X Scope no longer has its own X This is called Global Data since it can be seen by everyone and should be avoided if you can Most programmers consider this dangerous since it is hard to know which SUB might change a global variable You can also make a variable global to all SUBs from the Main Module by adding a DIM SHARED to the main module before you set X to 15 DIM SHARED X XxX 15 Scope PRINT Main Module says X This makes it easier to see which variables are global since they can be found in the Main Module The problem is that this makes a variable global to every SUB in your program Usually only some SUBs need to see a global variable It is better to use SHARED within your SUB in that case Object Oriented Programming When you start worrying about SUBs and the Main Module sharing variables you are probably ready to begin learning Object Oriented programming Object Oriented programming makes it easier to share variables between SUBs and still write code that is easy to understand Visual BASIC Java and C a
57. t will last This program makes a 1000Hz beep for about 1 second SOUND 1000 18 SOUND is good for making sound effects Here s a bomb dropping FOR I 4000 TO 1000 STEP 5 SOUND I 1 NEXT I If you want to play a song PLAY is exactly what you need Try this PLAY e8 d8 c8 d8 e8 e8 e4 PLAY is like a little programming language inside of QBASIC e8 means play an eighth note e If you are familiar with sheet music this will make sense Here s a scale PLAY c8 d8 e8 f8 g8 a8 b8 gt c4 The gt greater than sign means go up one octave There are many more special commands in PLAY Check the QBASIC help for a list of all of them PLAY and Triplets Here s a familiar tune that uses a trick to do triplets LAY T180 lt d8d8d8 T120 g2 gt d2 LAY T180 c8 lt b8a8 T120 gt g2d4 LAY T180 c8 lt b8a8 T120 gt g2d4 LAY T180 c8 lt b8 gt c8 T120 lt a2 gt Pl Pl Pl Pl Since PLAY doesn t do triplets you have to modify the tempo to get the right rhythm PLAY begins with a default tempo of T120 which means 120 quarter notes per minute In the above song we switch to T180 which is the triplet tempo for T120 By multiplying our tempo by 1 5 we get the triplet tempo When the triplets are done we switch back to the regular tempo You can see in the above example that we switch back and forth between the main tempo T120 and the triplet tempo T180 several times as needed As with everything there
58. the file before the program starts and write the file back out when the program is finished We will save the user s name and the number of times the program has been run in this file The code to do this is a bit more complex than what we ve done so far This is because QBASIC handles file errors in a strange way Our program must handle one file error The first time it is run there will be no registration file for it to read So the OPEN will fail We have to handle this or our program won t work If there are any problems QBASIC will jump to ErrorHandler below ON ERROR GOTO ErrorHandler This is the error code that is filled in by the error handler DIM ErrorCode AS INTEGER CLS Always reset this before doing something you want to check ErrorCode 0 Try to get the name and run count from the file OPEN register txt FOR INPUT AS 1 Tf the file wasn t found IF ErrorCode 53 THEN Get the name from the user INPUT Enter your name to register this program Name PRINT Thank you Name And set the run count to 0 RunCount 0 ELSE Get the user s name and the run count from the file INPUT 1 Name RunCount CLOSE 1 ND IF zal RunCount RunCount 1 PRINT This program is registered to Name D P PRINT This program has been run RunCount times RINT We hope you have enjoyed it Save the name and run count
59. to write to a file while a program is running so that you can look at what happened later This is called logging We can use the APPEND option in the OPEN statement to open a file and simply keep adding to the end of it OPEN logfile txt FOR APPEND AS 1 PRINT 1 Program Run TIMES CLOSE 1 CLS INPUT What is your name NameS PRINT Hello Names OPEN logfile txt FOR APPEND AS 1 PRINT 1 Program Stopped TIMES CLOSE 1 We ve logged two things in this program the program s start time and it s end time Run the program a few times then exit QBASIC and type notepad logfile txt That will show you what is in your log Input Files Ideas Fortune Teller using a text file as input This would combine file input with arrays Keeping Track of Things Let s say we want our program to remember who it is registered to We also want it to count how many times it has been run We could try something like this CLS INPUT Enter your name to register this program Name PRINT Thank you Name RunCount RunCount 1 PRINT This program is registered to Names PRINT This program has been run RunCount times PRINT We hope you have enjoyed it But that doesn t work Why Because QBASIC can t remember the value of the variables Name and RunCount from one run of the program to the next To fix this we need to use a file We can read
60. top Fortunately QBASIC handles making DECLAREs for us Unfortunately in larger programs it might put the DECLAREs someplace that looks ugly Fortunately you can move the DECLAREs anywhere you want as long as it is before the FUNCTION or SUB is first used and QBASIC still takes care of the rest Chapter 25 Data Structures Built In Types QBASIC offers five built in types Each of these types can be specified by a single character after the variable name You can also specify a type using a DIM statement It is important to pick the right types when you are writing a program The following descriptions of each type will help you make the right decisions Single Precision The single precision type handles numbers with decimals You can go up to seven digits with a single precision variable In a DIM statement use SINGLE to create a single precision variable The type character for a single precision variable is Unless you do something special any variable without a type character is single precision Here are some examples of creating and using single precision variables X 1 5 DIM Y AS SINGLE Y 2 1 Z 2 5 PRINT X Y Z Notice that the DIM statement can be used to tell QBASIC the type of a variable Then you don t need to use a type character for that variable String The string type handles strings of characters You cannot do math with string variables In a DIM statement use STRING to create a string v
61. we need to CLOSE the file to let QBASIC know that we are done Otherwise QBASIC might not write anything to the file at all The CLOSE statement only needs to know which file you want to close so it only requires the file number Reading from a file The following program will get the name and print it on the screen OPEN testfile txt FOR INPUT AS 1 INPUT 1 Names CLOSE 1 PRINT Name There are three main things that are different in this program if you compare it to the previous program 1 The OPEN statement uses INPUT instead of OUTPUT This tells QBASIC that we plan to get data from the file 2 The INPUT statement which you ve seen before is used to read from a file The 1 tells it that we want to read from file 1 When we ve used INPUT in other programs there was no 1 Without a file number INPUT gets information from the keyboard With a file number it gets information from a file 3 Instead of getting something from the user at the beginning of the program we display what was read from the file at the end with a good ol PRINT statement One thing that hasn t changed at all is the CLOSE statement We CLOSE file 1 so that QBASIC knows we are done with it While we probably won t lose any data if we don t CLOSE in this case it is still a good thing to do QBASIC can only open so many files so if you leave some open you might not be able to open any more Logging Sometimes it can be very useful
62. you then need to unzip it and move qbasic exe and qbasic hlp to c windows command Someone who is familiar with zip files can help you do this Windows 95 QBASIC is on the Windows 95 CD ROM Put the Windows 95 CD in your CD ROM drive It will pop up a window that you can go ahead and close click on the X in the upper right corner of the window DOS Or Windows There are two ways to get the QBASIC files onto your computer Using the DOS prompt is the fastest method but you need to know your CD ROM drive s drive letter e g d e or z The method described in the Windows Explorer section is a bit slower but you don t need to know the CD ROM drive s drive letter DOS Prompt You should already be at a DOS prompt from trying to start QBASIC This makes things easier I am going to assume your CD ROM drive is drive letter d If it isn t substitute the correct drive letter in the copy command below Type the following lt Enter gt means Press the lt Enter gt key c lt Enter gt cd windows command lt Enter gt copy d other oldmsdos qbasic lt Enter gt That should have copied qbasic exe and qbasic hlp to your computer Skip to the Finished section to check if all went well Windows Explorer If you don t want to try the DOS method Windows Explorer can also be used to get QBASIC on your computer We need Windows Explorer not Internet Explorer to copy the QBASIC files from the CD and into

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