Hello everybody! Ok now, actually I thought to write this book keeping in mind, the problems faced by the beginner programmers in Qbasic. Qbasic is an excellent tool to develop a programming concept in students. Actually it was developed for that very purpose only. But in spite of its simplicity, students often feel some problems during their studies. I don’t know its exact reason but I guess that the course books just focus on the theoretical studies and don’t actually develop the concept in students. A programming just doesn’t mean to find “LCM, HCF, Factorials, Prime numbers” and other calculations but the real meaning of programming is to directly communicate with the computer and make it perform some work.
I, being really interested in programming, had some explorations on the net and gathered some basic techniques of this programming language. And seeing the complications of the students during the course, I was inspired to write this booklet. Frankly speaking, QBasic is not that hard. But programming can be really a challenge. QBasic just develops a basic concept, it is not that standard language and programming is not only limited to Qbasic. You will find a lot more in the field of computers; this is just a beginning step. And also it depends on you that how much you want to go deeper into the programming concept. Anyways, I hope that you find it useful and handy. If you still face problems after completing this book then I am always in this world. You can just contact me at my mail address i.e.Pro_science108@yahoo.com. Hope you will enjoy it because I have, my best, tried to use simple language and techniques. And yes, being a student myself I can’t assure you that this booklet is 100% error free. But I have tried my best to correct all the errors like spellings, grammar and others. What else can you expect from a student? If you could catch any of them and point out the mistakes then you have got all sort of rights to contact me and inform me about those bugs. Also, if you have some other suggestions for me then you are always welcomed. Don’t forget to write a feedback.
Last but not the least, the legal stuffs ( Boring!). You can distribute this booklet to any of your friends, students or your children (And please don’t forget to mention my small name, will you? ) but please never try to misuse it for any commercial purpose. I hate these types of guys, you know!
I have written this book assuming that readers have some little previous knowledge of the programming language (QB). But complete beginners can also take benefits from this book. However those with little previous knowledge can have advantage. The perfect scenario will be that you have already learnt QBASIC but you don’t quite know about how to use the functions and you haven’t got the programming language well.
This book has nothing related with advanced topics in QBASIC like Modular programming, File Handling, Graphics and Multimedia etc. If you have already learnt the basic techniques then you got this book accidentally and should distribute to one who needs it more.
Pravesh Koirala Prasanna Koirala Family members Someone else
Diwaker Jha(Hey I wrote this book!)
(For inspiration and support)
(For their support)
(Cause he is the real source of inspiration for me. I don’t want mention his name)
(A fantastic person, nice friend, and the one who lead me deeper into computers)
Finished this Book! Please write a feedback to me. Your feedback will prove to be an inspiration to me. If you want some more QBASIC stuffs then you can always search internet. Also, I plan to write next part of this book as “Advanced QBASIC Stuffs” covering concepts like File Handling, Modular programming, Graphics and Sound, Game programming in QBASIC etc etc etc. Let’s hope that it will be completed soon. Thanks!
Well ready for some QB lessons. Ok now try to learn some fundamentals before actually starting programming concept. Qbasic is a character programming language. (What does it mean?). It means that you cannot implement the windows components like command button and scroll bars that you generally use. Anyways no matter what it is but we have to learn it right? Now you will find that you need to calculate a value like adding, subtracting, divisions etc even for a small program. If you have already programmed a simple application then you ought to know that for multiplication you follow the following steps.
QBasic calculation Human Calculation
CLS 3 x 4 (3 times 4 or 4 times 3) A = 3 i.e. 3+3+3+3=12 or 4+4+4=12
B = 4 thus, 3 x 4 = 12
Print a*b
End
Umm, let’s think now. What is the difference between this calculation and our human calculations? We have generally mugged up the table of up to 20 even more. Thus it’s in our mouth that 3 into 4 equals 12. But the story is different in case of QBasic. First we store 3 in A and 4 in B and we used print a*b. I hope you know the simple functions like Print, CLS and End, If not then wait for Chapter 3 :. Anyways let’s see what happens in this case. First of all the value 3 is stored in one location of Ram and value 4 in another location. Now it will straightly travel into the processor’s ALU (calculation unit). Since, computer is a digital system and it have no techniques like ours, thus, first of all it converts 3 and 4 into binary that is 11 and 4 is 100. Now it will perform binary multiplication (I hope you do know the binary calculations) there and store the result into its memory (No, not RAM, CPU have its own store place called registers). Then it converts the result into decimal and sends the value into a location in Ram (yes, another location!) and then Qbasic access it and prints into the screen. Phew! A long process, isn’t it? If you were said to do it then I think it must cost you minimum 50 seconds or more for the longest one. But imagine, the computer does it in a trillionth part of a second, isn’t it amazing! Let’s have a quick graphical recap.
A 3B RAM CPU 4
RAM
Qbasic Screen
So next time onwards you will always respect Qbasic, will you? Anyways, since you have learnt the calculating concept, you have rights to ask me that why this is important? For its answer you must wait for the next chapter. If you still don’t have a proper idea about this topic then I urge you to read it again and again because this is very important chapter that teaches you a good formula for neat programming.
*Some good practicesHere are some of the good practices that you can use in your program.
1) Always declare the variables with Dim command before using them. (More details in next lesson)
2) Always try to write remarks in your program using REM function or ‘ character. Writing remarks makes it easy to understand your program for yourself and other programmers.
3) While writing conditional statement and loops first write their opening and closing command and then insert the statements in between them.
4) Try to select the most suitable loop for your program.
5) If you are writing a lengthy and complicated program then try to break it into small sub procedures.
6) Always select the variable name that is most suitable for the calculation and easy to remember. E.g. If you want store average marks of students in a variable then try to use variable like Avg_Student or Avg_Mark etc.
7) While using Print or Input statement always try to give a proper message to the user otherwise your program couldn’t interact with the users well.
*Using Help
QBASIC is provided with a manual. If in your program anything goes wrong then you are prompted with an error message. If anything like syntax error happens then you can always check out the manual. Just place the cursor below the problem area and press F1 key. That will display the help related to that very command.
*The translator
You will find that in most of the topics I have mentioned about translator. I think many of you know about it. If you don’t then Good! As I mentioned earlier, computer is a digital machine and it knows only 0 and 1. Then the question comes that how does the computer follows our English instructions like Print, End, CLS etc? It’s because the English command that you type on the QB editor, is translated to 0 and 1 via either a Compiler or an Interpreter. These Compiler and Interpreter are called translator software.
*Statements
The statements, in QBASIC, are the operations that give some result. E.G. a=4, b=b*5, Print “hello” etc
Let’s recall the simple program that we made in the first lesson.
CLS
A=3
B=4
Print a*b
End
Now, I think that you do know about the variables and constants but anyways you will have a clear concept about those in this lesson. Lets see “A=3” we already dealt that what it does. It simply stores the value 3 in a location in RAM. Then what is the importance of “A”? Its answer is, the location in which the value 3 will be stored in the RAM will be represented by the keyword “A” so that when you want to retrieve the value of A from Qbasic then the system will search all the values stored and used by the program. Then it will have three locations A, B and another one (I know that you are amazed but yes there is another location with a value. What is it can you find? If you can’t then don’t worry, I will tell you about it in the last part of this chapter). Within the three locations the system will match the keyword that is A. Now when it confirms the value then it transfers it into the QB and QB displays it into the screen.
Phew! Again a long process just to recall a simple value, isn’t it? Now think for a while, why in the world is this process important and being mentioned? Imagine that you will try to retrieve the value of one variable and then you get the value of another. This can really be dangerous and it is simply not good. Well we are lucky that the computer does it all otherwise it would have been a tedious task to manage all the locations and values.
And can you answer that why the hell “*” is used instead of “x” for multiplication. Answer is simple, it is because you might want to have a variable “x” and this will create a lot of confusion. Well the developers of the QB are really smart, aren’t they? While determining a variable following things should be considered.
A variable has its two characteristics, its type and data hold by it.
*TYPES OF THE VARIABLE
Consider,
A=3 and A=0.003
In both the cases, there is used a same variable A but there is a lot of difference between their types A=3 represents that A is a variable used for storing an integer type value but on the contrary, A=0.003 represents that A is used for storing a decimal or floating type value. And yes, each variable has its own type that must be declared. The declarations can be carried out by the Function DIM. E.g.:
Dim a as Integer
Dim b as Long
Dim c as String
Dim a (5) as integer
Note the point that a, b, c are the variables and the keywords “Integer”, “Long”, “String” are their types. The characteristics of the types can be found in any course book. I suggest you to go through it. In summary, each variable has its own memory requirement.
Now the big question comes that though we haven’t declared the variables A and B in our previous program, how does the program handles the memory for it? And the small answer is; all the non declared variables are thought to be a numeric variant by the translator. But what is a variant? Variant is also a type but it consumes comparatively a large space in the memory. So, it’s not a good practice to use them more often. However, in small programs they can be used. EG:*Non declared or implicit variables E.g.:
A=3
Print a
A=0.03
Print a
End
Output:
3
0.03
*Declared or explicit variables Dim a as Integer
10: A=3
20: Print a
30: A=2.03
40: Print a
50: End
Output:
3
2
What! A 2! But hey, I said that I want to print a 2.03. Maybe the translator has gone mad! No, it is not the translator. As soon as you run your program, the translator translates the program to machine codes from top to bottom. The translator is instructed that the variable A is an integer and so, it occupies memory space for integer. Up to step 20 it runs smoothly but as soon as it encounters the next step i.e. (A=2.03) then it thinks for a while, “Umm, let’s see what we have, A=2.03. What? Oh god! What’s the programmer trying to do? First he says reserve the space for integer and then wants to keep a floating value 2.03. He must have gone mad! Anyways better I store only the integer 2.”
And so the translator doesn’t store any floating value and variable A becomes 2. So Einstein, from next time onwards never try to store a wrong value in a wrong type. It can really annoy the translator and moreover can effect a mathematical calculation.
*String Type Value
A string type value resembles a character sequence of up to 32,767 characters and always kept inside the double quotation in not only QB but in other higher programming language too. Strings are handled differently by the memory (RAM). So, if you try to store string in a numeric variable and vice versa then system will feel really . Let’s have an example.
Example-1 Example-2 CLS CLS
A = “HELLO” Dim A as String Print A A= “HELLO” End Print A
What do you think what is the output of Example-1? If you thought about an error then you got it! Certainly, there will be an error i.e. “Type Mismatch”. Well, previously the translator did correct our error because it was related to numerical type mismatch but as I told, the string is completely different from the number in relation to its storing process. Do you know something about ASCII? You must know! There is a standard code for each of character. So when you store some string values then RAM will not actually store the character but its ASCII instead.
But in Example-2 we have already instructed the translator that we need a space for string value represented by the variable A. So there will be no any complications.
*Signs used for types
Imagine that you are designing a small program and you don’t want to spend time writing declarations for variables (However writing declarations is a good practice:.) Then you have the options to use some special signs that will tell the translator about the types of the variable. E.g.:CLS
A$= “Pravesh” ‘Instead of declaring A as string you can directly use signs
Print A$ ‘But remember you must always assign the sign in the program with that variable End
*Following are some of the signs that can be used for different var(variable) types i) $ String
ii) % Integer
iii) ! Single Floating Point
iv) # Double Floating Point
v) & Long Integer
*Declaring a default Type
Now think for a while. You want to work only with one type i.e. string. I mean that you want to use only string variables in your program. Then there are three ways.
i) Declare all variables that you want to use as String
ii)Use sign $ for each variable
iii)Declare the default type as String
I am sure that out of these steps you are familiar with the first two. So, lets learn how to declare a default variable. By default, in Qbasic, each variable is a numeric variant unless declared using Dim statement or using signs. But we can declare any other type as default according to our wish using the DEF-Type keyword. E.g.:- DEFStr A-Z
Lets break the statement. DEF + Str + A-Z are our results. Clearly, DEF is a function used to declare the default type. Str is acronym for String and A-Z is the range. What this function does is, it declares all the variables from A to Z as String unless separately declared using Dim or any sign. Let’s have a short example. CLS
DEFStr A-W
Dim C as integer V= “Hello World!” C = 8
D! = 9.09
Print V , C ,D%
End
‘Now lets declare all variables from a to w as string
‘Lets separately declare C as integer
‘Put “Hello World” in variable V
‘Put 8 in C
‘Store 9.09 in D!
‘Print all vars
Understood? What! No? Ok ok don’t panic, Lets deal it in detail. We declared all values from a to w as string. So, we need not use $ sign with the variables now onwards. But wait, we also declared c separately as an integer. And why we have used D! while storing 9.09 in it? So confusing right? Answer is, we are storing an integer value in c i.e. 8. But since the default type is string, thus, Qbasic would have treated it as a string and you know that 8 is not a string so there would have an error. For D we have stored 9.09 and again the QB would have tried to store it as a string but since we provided it with the symbol ! so the translator will now store it as a single precision. Clear as mud, right?:
*CONSTANTS
Since you are now clear with the variables then lets head towards Constants. You already know that variable is a location in memory that stores a data. And Constant is that very data which is being stored. E.G.
A% = 5
B% = 10
With this simple command, the following things happen inside the memory.
0 0 0 5 0 0 0 0 0 0 0 1 0 1
0 0 0 0
0 0 0 10
RAM B Bits
I think that since you began to learn computer, you were taught about 1 byte is equivalent to 8 bits. If you were not quite clear about that then the figure illustrates it all. Bit is the smallest part of memory. And the group of 8 bits make 1 Byte.
Every thing is alright except that all other locations(or bytes) are 0. Do you know that the memory stores the data in form of electric charges?
Now when you store 5 in A then translator occupies a memory location and system charges the memory electrically and 5 is stored in form of electricity. But consider this small program. CLS
Dim C as integer
Print C
End
What do you think about the output? Certainly, there will be a zero. You did declare space for C but you forget to store any value. It means that the memory won’t be charged and as a result you will get a big 0. But in other programming language like C++, the default value of a variable is undefined.
*Updating the value of constants during program execution
In QBASIC the value of constants can be updated during run time. Well, if it can be changed then why is it named Constant? Strange, right?
Anyways, updating the value makes it possible to carry out different calculations. E.G CLS
A=5
A = A+2
Print A
End
I think that I need not mention what happened here.
*Updating Variable with loops For updating variable repeatedly, we must use it with loops. Loops are described in forthcoming chapters.
*What was that another location mentioned earlier?
Well I mentioned about three locations at the start of the chapter but there were only two viz. (namely) A and B. Then what am I gone mad? No certainly not, if I were mad then how could have I wrote this book. Anyways, So what was that third location? The answer is, after the calculation of 3*4 the result i.e. 12 is also stored inside the RAM. So, it is also a location, isn’t it?
So, we came to the end of this chapter. See you in next chapter. Oh! I was about to leave without giving you an information. See, how dumb I am! The thing that I wanted to inform you was that I didn’t mention some more topics about the variable types like User-defined types. Remember what I said earlier, it depends upon you that how deeper you want to go inside the programming concept. So, if you want to explore more then just check out some other books and explore. Otherwise, leave it!
The real programming starts from this chapter. Let’s first deal with some common QBASIC Functions. *The CLS Command
CLS is an abbreviation for Clear Screen. As its name defines, it is used to clear the output screen. CLS also have some parameters (Some values that needs to be given to the function to ensure proper results). But CLS can be also used without it which clears the whole screen. If you want to know about those arguments then discover yourself!
*The Print Command
Print command just prints the value of a variable or some message to the output screen. The two different things to print should be separated by a “,” or “;”. By default the print command supplies the carriage return (an instruction to computer to come to next line) unless used provided with ; at the end. “?” can be used instead of Print command CLS
A=5
Print A; “Is the value of A” End
Output
5Is the value of A CLS
A=5
? A
Print “Is the value of A”; Print “ Got it!”
End
Output
5
Is the value of A Got it! CLS
A=5
Print A;
Print “ Is the value of A” Print “Got it!”
End
Output
5 Is the value of A
Got it!
Analyze all the three programs and their output carefully. There are many questions to be answered like:- In 1stprogram “5Is” is joined but in program 3, “5 Is” is separate. Remember the space you give in the string message is also counted and printed.
*The End Command
End command is simply used to terminate the program. It deletes all the value of variables from memory and closes all opened files and devices (Advanced topic). Another alternative of End command is SYSTEM which ends the program and returns to the system as well.
*The Input Command
The input command allows user to input a value in variable during run time. You can give messages to the user that will make it more user friendly. The value type that user inputs must be similar to the variable type that is used to store the value. A “;” or “,” should be used to separate the different parts of input statement. And multiple values can be entered. E.G:
CLS
Input “Your name and age ”; nam$, age ‘Here name is string type so nam$ is used. Print “Your name is”;nam$ Print “Your age is ”;age End
Output
Your name ?Pravesh,19 Your name isPravesh
Your age is 19
‘Consider that no space is used with the print command. ‘And space is given with another print command
So to clarify that what you want from the user, message must be given in a proper way. A simple program to ask user two value during runtime and print their product CLS
Input “Enter two values separated by a comma ”;a , b
Res = a*b
Print “The product of the two values is ”;Res
End
Output
Enter two values separated by a comma ?2,3
The product of the two values is 6
*Conditional Statement (If..Then..Else)
Imagine that you want to test a condition that whether the age of the user is above 18 or not. Then you can implement following codes.
CLS
Input “You age ”;age
If age>18 then print “You are adult” else print “You are not an adult”
End
Equality
When you test a value in QBASIC then either you will get true or false. True represents 1 whereas False represents 0. Any non-zero value is considered as True in QBASIC.
If.. then..else command can also be defined through its name. Its syntax is:If (condition=true) then statements1 Else statements2. The conditional operators are greater than(>), less than(<), equal to(=), greater or equal (>=), less or equal (<=), not equal(<>). All the above conditional statements can be easily understood because we have been using it in math since childhood, haven’t we?
If.. then..Else command is of two types. Single line and Multiline. The above you saw was single line. Lets consider a multiline one.
CLS
Input “Any number ”;no
Res = no mod 2
If res=0 then
Print “The number you entered is even” Else
? “The number you entered is odd” End if
End
Output
Any number ?8
The number you entered is even
Multiline If statement has following syntax If condition is true then
Statements
Else
Statements
End if
‘Divide no by 2 and check the remainder
‘If remainder is 0 or number is perfectly divisible by 2 then
Always remember that the multiline if statement should be terminated by End If statement. It tells the translator that the condition is over and normal operation can be carried out. Mod used in the program is an abbreviation for modulus. It simply returns the remainder value. 8 mod 2=0, 8 mod 3=2 and 2 mod 3=0 etc.
Multi conditioned if statement is also equally important. It is generally used to test multiple conditions. For example, if you simply want to operate two numbers (addition, multiplication, division, subtraction etc) then you need to first get two values from the user and also what he wants to do with that two values.
The syntax of multi conditioned If statement is: If (statement1) is true then
Operations
Else if (statement2) is true then
Operations
Else if (statement 3) is true then
Operations
Else
Operations
End If
Remember, End if should always be supplied at the end of the multi conditioned If statement. E.g.:
CLS
Start:
Input “Please supply me with two values”; val1,val2
Print “What do you want to do with these values? “
? “1.)Addition”
? “2.)Subtraction”
? “3.)Multiplication”
? “4.)Division”
Input “Enter your choice “;choice
‘Starting of the condition
If choice=1 then
Result = a + b
Else if choice=2 then
Result = a-b
Else if choice= 3 then
Result = a*b
Else if choice=4 then
Result = a/b
Else
Print “Please enter a valid choice”
Goto start:
End if
Print “The result of your operation is “; Result
End
Output
Please supply me with two values ?5,6
What do y
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