• .MDB - Access Database
• .MDE - Protected Access Database

 Access VBA File Extensions (.MDB)

.asp is the default extension for Active Server Pages (ASP) although some developers will change the default extension in an effort to add an additional security level. Although there is no clear standard for include files, using .INC is common but you must make sure that .INC files are not executed nor displayed.

Common source code file extensions include:

• .SLN - Solution File. Contains solution specific information such as links to the projects within this solution.
• .CSPROJ - C# Project File. Contains project specific information. When you add a file containing one or more classes, it is added to this file.
• .CS - C# source file.
• .Designer.CS - C# form file (a text resource file).

//Sample code snippet from the .csproj project file:

<ItemGroup>
  <Compile Include="Cyborg.cs" />
  <Compile Include="Cyborg600.cs" />
  <Compile Include="Form1.cs">
    <SubType>Form</SubType>
  </Compile>

  //...

Important standard C++ file extensions:

• .CPP = C++ Source file. Your startup source file will have a main() routine.
• .C = C source file (sometimes used for C++ source files too).
• .H = Header include file.

Some important Visual C++ file extensions:

• .SLN = Visual Studio.Net solution
• .VCPRJ = The Visual C++ project file. See Project Files and Makefiles for more information.

Some important C++Builder file extensions:

• .BDSPROJ and .CBPROJ = Project file.

 Ref: http://msdn.microsoft.com/en-us/library/3awe4781(VS.80).aspx

The C++/CLI standard file extensions are the same as standard C++. Important C++ file extensions:

• .CPP = C++ Source file. Your startup source file will have a main() routine.
• .C = C source file (sometimes used for C++ source files too).
• .H = Header include file.

Some important Visual C++ file extensions:

• .SLN = Visual Studio.Net solution
• .VCPRJ = The Visual C++ project file. See Project Files and Makefiles for more information.

 Ref: http://msdn.microsoft.com/en-us/library/3awe4781(VS.80).aspx

Paradox for Windows has two primary file types: source files and delivered files:

Source Files
Source files in Paradox are binary but can can be opened in later versions of Paradox and even in earlier versions if you don't use any new features.

• .FSL = Form
• .RSL = Report
• .SSL = Script
• .LSL = Library

Since Paradox source files do not compile to an EXE, Paradox developers tend to use a startup form or script to start the application.

 ObjectPAL File Extensions  

Delphi Prism common source code file extensions include:

• .SLN - Solution File. Contains solution specific information such as links to the projects within this solution.
• .Oxygene - Project File. Contains project specific information but this is not the Delphi-like project file Delphi developers are used to. This is the VS.Net project file.
  
• Program.pas - This is the Delphi-like .dpr project-equivalent file and contains the Main method which is the entry point for the executable. All .NET projects except for DLLs needs one.
  
• .pas - Delphi Prism source file (same extension as Delphi for Win32).
• .Designer.pas - Prism form file (a text resource file).

The customary primary source file extension for Java code is ".java" which could contain anywhere from a single class to the entire source code.

Other important files:

• .JAR - Java archive file (compressed code file). Archive that contains multiple Java files and is compressed using .ZIP compression; stores Java classes and metadata and may be digitally signed; runs as a program if the Java Runtime Environment (JRE) is installed on the computer.
• .CLASS - compiled source code which are platform-independent. If a source file has more than one class, each class is compiled into a separate .class file. These .class files can be loaded by any Java Virtual Machine (JVM).

 Java File Extensions (.java)

.js is the common standard for browser-side JavaScript and .jsp is the common standard for server-side JavaScript.

.pl is the traditonal default extension for Perl although some developers will change the default extension in an effort to add an additional security level and .cgi is still popular as a Perl associated extension as well as .plex and .aspl.

• .pl - Perl
• .cgi - Common Gateway Interface
• .plex - Perl Executable
• .aspl - Active Server Perl

.php is the default extension for PHP although some developers will change the default extension in an effort to add an additional security level. If your code is tied to a particular version of PHP then some developers at the major PHP version number to the extension as in .php3, .php4, .php5, etc. 

.phtml is also sometimes used especially for files that contain both HTML and Perl code.

• .BAS = VB source code file.
• .CLS = VB class file (one class per file).

Common source code file extensions include:

• .SLN - Solution File. Contains solution specific information such as links to the projects within this solution.
• .VBPROJ - VB.Net Project File. Contains project specific information in XML. When adding a file, it is added to the project file.
• .VB -VB.Net source file.
• .Designer.VB -VB.Net form file (a text resource file).

//Sample code snippet from the .vbproj project file:

<ItemGroup>
  <Compile Include="Cyborg.vb" />
  <Compile Include="Form1.vb">
    <SubType>Form</SubType>
  </Compile>

  //...