PDF | On Aug 1, , Akinola Adeniyi and others published QBASIC QBASIC Programming Without Stress. Book · August with 55, Reads. Microsoft QuickBasic and QBasic are very popular programming languages for beginners. BASIC and Visual Basic Programming. QBasic (Faraaz Damji, et al). in QBasic. This document is meant to get you started into programming, and assumes you have some experience with computers and with Windows 95 (or 98 .
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In other words, upper and lower case are ignored. Here's an improvement to a previous program. How are you today? How about with a FOR loop? The second argument is the character you want to repeat.
To make strings of letters, computers convert letters to numbers so they can work with them. We've already seen this in a previous chapter. ASC takes a character and tells you its number. If it finds the string, it will tell you where it is. This lets you explain what you've done to someone else who might read your program later.
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 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. Using a constant makes the program easier to read and understand. It also keeps us from making mistakes when copying. Chapter 25 - Sub-Procedures SUBs When programs get big, you need to break them into smaller pieces that are easier to work with.
Other programming languages have other names, like procedures, subroutines, or subprograms. Select "View SUBs 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. This will jump you to the view of the new SUB. From the menu, select View SUBs 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. 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. 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. When we do this, Radius is called a "parameter" or "argument" to our SUB. Would they be the same variable?
Quality Notes, Study Materials, Academic Contents, Videos and Games
Let's find out. What happened? Scope said "0" because to Scope, X was a new variable. Scope's X and Main Module's X are different variables. If you need to share variables, you can pass them as arguments to the SUB. Introduce global data and statics last instead of functions last.
Also write a GOTO chapter and put it at the end of the book as well. 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.
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. Object Oriented programming makes it easier to share variables between SUBs and still write code that is easy to understand. Then we will get the behavior we expect. Functions Functions are just like SUBs, but they return a value. Why does it do this? It would think it had found a syntax error and the program would stop.
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. The type-character for a single-precision variable is "! Unless you do something special, any variable without a type character is single-precision. 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.
Integers may range from to 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. Long-Integer The long-integer type handles numbers without decimals.
Long-integers may range from to 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. You can go up to fifteen digits with a double-precision variable. Double-precision variables are used where very accurate math is needed.
The type-character for a double-precision variable is " ". Arrays are very similar to variables, but they hold more than one thing. You can think of an array as a list. Arrays can also store numbers.
If you go over 10, you'll get a "Subscript out of range" error. 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.
FullName; ": "; Friend. DIM makes a new variable of that type. When we work with types, we use the variable name, followed by a dot ". However, a TYPE cannot hold an array. FullName; ": "; Friends I. 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. The following program will do exactly what the previous program does.
QBasic/Full Book View
It only pays attention to them when it finds a READ statement. You might need to load several different arrays in your program.
A label is a name like "Names:" or "Values:". Here's a new version of the database example using DATA statements this time. FullName, Friends I.
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. 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.
You can use Notepad to find it and make sure your name is there.
That can be a little tricky. The "type" command at the DOS prompt copies the contents of a file to the screen. You could also try this: notepad testfile. 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. 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 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. The 1 tells it that we want to read from file 1. With a file number, it gets information from a file. 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.
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.
QBasic Techniques for Beginners
Logging Sometimes it can be very useful to write to a file while a program is running so that you can look at what happened later. This is called "logging".
OPEN "logfile. 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. This top level module is called main module.
The main module is the controlling section of a modular programming. Sub- module : Sub- module is a program which is written under the main module.
A modular program may have one or more than one sub- module. It is called sub- program. Qbasic is also known as modular programming language because it allows the user to divide program into manageable and functional modules or blocks with the help of sub procedure and function procedure. Merits of Modular Programming It reduces the program code.
It is possible to use single module in different places. It makes debugging easier. It makes the maintenance of the program easier. It reduces the chance of changing the value of variable accidentally. They are as follows: Sub Procedure : A sub procedure is a small manageable and functional part of a program that performs specific tasks and does not return any value to the calling module. A sub program is written with SUB Some important features of sub procedure are as follows: It does not return any value.
Sub procedure name can't be used as variable. Arguments can be passed to the sun program by reference or value. Function Procedure : A function procedure is small manageable and functional part of a program that performs the specific tasks and returns a single value to the main program or calling module.
Some important features of function procedure are as follows: It returns a value.Take blue which is 1 and add 8 and you get 9 which is bright blue. The argument can be passed to a procedure either by reference or by value method. You could also try this: notepad testfile. Scope no longer has its own X. Then we will get the behavior we expect. The constant or variables enclosed in the parentheses of procedure call statement and that are supplied to the procedure are known as arguments.
Constants look and act like variables, but they cannot be changed.
Programmed Lessons in QBasic
Let's try to change the value of Age. Each of these techniques has its advantages and disadvantages. Here, we will discuss on inputting statement, outputting statement, Assignment statement, and Goto statement.
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