FreeBASIC

FreeBASIC is a free/open source (GPL), 32-bit BASIC compiler for Microsoft Windows, protected-mode DOS (DOS extender), Linux, and Xbox.

FreeBASIC allows a high level of support for programs written for QBasic, by using the "QB" dialect. Many programs written for QBasic will compile and run in this mode without any changes needed. However, most substantial programs will need changes to be made before they can be compiled using the default dialect.

Features

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Syntax

FreeBASIC syntax attempts to stay as close to the BASIC syntax as possible, specifically that of QuickBASIC. Although the syntax attempts to stay compatible with its predecessor, FreeBASIC follows modern standards and coding practices. Standard procedural features, along with object oriented features such as types as objects, operator overloading, function overloading, namespaces, etc., have been added in FreeBASIC.

FreeBASIC's lines end when the end-of-line characters are found, or with a colon. Because of this, lines don't have to have a special character (such as the semicolon in C) to notify the compiler of the end of line. Multiple statements may be written on one line by separating each statement with a colon :.

FreeBASIC supports block commenting along with end of line remarks. Full line comments are made with an apostrophe ', while blocks of commented code begin with /' and end with '/.

Compatibility

FreeBASIC is a successor to the QuickBASIC programming language. Changes were made during development to keep FreeBASIC compatible with modern utilities, and facilitate advanced programming features. In order to keep the compiler moving forward, GCC compliant, and to also retain the ability to use a QuickBASIC compatible language, the -lang option set was created.

- When choosing Language Set FB (-lang fb as a command-line argument), all of the new features that FreeBASIC offers are available, and the "hackish" features from QuickBASIC (that were incompatible with modern programming practices) are disallowed.

- Language Set FB-Lite (-lang fblite) provides access to most of the new, non-object-oriented features of FreeBASIC, but allows a coding style similar to that of older versions of BASIC. Syntax rules, such as allowing implicit variables, suffixes, GOSUB / RETURN, numeric labels, etc., are permitted in this lang option.

- Language Set QB (-lang qb) is similar to -lang fblite, but is more focused on specifically replicating QBASIC-like behavior. -lang qb is designed to make it easier to run programs originally written for QBASIC, and is useful in cases where -lang fblite is not compatible enough.

Example Code

As in QBasic, a program to write a line of text to the screen can be done with a simple statement:

print "Hello, World!"

However, FreeBASIC adds many object oriented features such as methods, constructors, dynamic memory allocation, properties and temporary allocation.

/'A Vector motion class'/
Type Vector
	W as Integer
	H as Integer
	Declare Constructor (nW as Integer, nH as Integer)
End Type

Constructor Vector (nW as Integer, nH as Integer)
	W = nW
	H = nH
End Constructor

/'Create an object class'/
Type Object
	Private:
		X as Integer
		Y as Integer
		Movement as Vector Pointer
	Public:
		/'Create public methods, including a destructor for automated cleanup'/
		Declare Constructor (nX as Integer, nY as Integer)
		Declare Destructor ()
		Declare Sub SetMotion (Motion as Vector Pointer)
		Declare Sub Move ()
		Declare Property GetX as Integer
End Type

/'Set initial coordinates'/
Constructor Object (nX as Integer, nY as Integer)
	X = nX
	Y = nY
End Constructor

/'Clean up allocated memory'/
Destructor Object ()
	delete Movement
End Destructor

/'Set the motion Vector'/
Sub Object.SetMotion (Motion as Vector Pointer)
	Movement = Motion
End Sub

/'Move the object based on its motion Vector'/
Sub Object.Move ()
	X += Movement->W
	Y += Movement->H
End Sub

/'A getter for X, as it's private'/
Property Object.GetX as Integer
	Return X
End Property

	/'MAIN CODE'/

/'Create a new instance of Object at coordinates 100, 100'/
Dim Player as Object = Type<Object>(100, 100)

/'Dynamically allocate a new Vector object
moving left 10 units and down 5'/
Player.SetMotion(new Vector (-10, 5))

/'Make the Player update its location'/
Player.Move()

/'Display new X, 90'/
Print Player.GetX

/'Because Player is a local variable, it's destructor is
called at the end of scope automatically'/

Graphics library

FreeBASIC has a built-in 2D, software graphics library to be QuickBASIC compatible, which provides the user with simple graphics primitives (such as rectangles, lines, and circles), blitting, and additional features which weren't present in QuickBASIC's graphical library. The library itself is not OS dependent, so code is portable across platforms with the library.

Although the library is built-in, it is only included if one chooses to use it, which is done simply by including a call to the FBgfx Screen command. Common libraries such as OpenGL + Creating a Window with your API (Windows, Linux, Etc.) for hardware acceleration can be used without interfering with the FreeBASIC graphics library.

Future development

FreeBASIC continues to make development progress toward its goal of being a GCC front-end, which would allow many features found in C++ and other object-oriented programming languages, portability to nearly any modern system, and advanced optimization techniques.

With the release of version 0.17 object oriented programming (OOP) was introduced adding classes, extending the basic type. Further implementations are expected.

During the 2007 Sourceforge awards, FreeBASIC reached the shortlist of nominees for best user support.

External links

• Official website
• Official forum
• SourceForge homepage
• FreeBASIC Documentation in Wiki Format
• FreeBasic package for RPM-based distributions
• FreeBasic packages for DEB-based distributions