File extensions

Here are the file extensions that are used when developing programs in Pascal. In most cases, these are extensions used by the IDE (Lazarus) and the compiler (FPC).

Lazarus

Project files

extension	description	help	format
.lpg	Lazarus Project Group file	Project Groups	XML
.lpk	Lazarus Package file (contains package-specific settings)	Lazarus Packages	XML
.lpi	Lazarus Project Information file (contains project-specific settings)		XML
.lps	Lazarus Project Session file	Project Options	XML
.lpr	Lazarus Program file, contains Pascal source of main program		pascal
.lfm	Lazarus Form file - contains all components and their properties. The source code of the form is located in the PAS-file of the same name.		text
.pas	Unit with Pascal code. It may also contain the code of form (stored in the LFM-file of the same name).		pascal
.pp	Pascal code		pascal
.inc	Include file. Contains a part of Pascal code that can be "included" in the program by the {$i} directive. Not to be confused with INC-files of other programming languages that use the same extension.	$include	pascal
.compiled	Compilation session for a project		XML
.ppu	Unit description file. Not to be confused with the compiled unit, which has the extension ".o"	[1]	binary
.o	Compiled unit. Is the result of compilation by FPC (Free Pascal) or any other compiler (e.g. GCC for C++).		binary
.or	Object resource, automatically generated from {$R} directive		binary
.a	(1) Compiled unit, code part for smartlinking (on some platforms) (2) Compiled code from other compilers (e.g. gcc) linked into a static library		binary
.lrs	Lazarus Resource file (this is a generated file; not to be confused with a Windows resource file)	Lazarus Resources	text
.lrt	Lazarus Resource string Table created when saving a LFM-file and i18n is enabled. It contains the TTranslateString properties of the LFM-file.
.rst	Resource String Table created by the compiler for every unit with a "resourcestring" section	Getting translation strings right	text
.rsj	Resource String table in JSON format created by FPC 2.7.1 for units with "resourcestring" section	Using resourcestrings, [2]	JSON
.rc	Resource script	Lazarus Resources	text
.res	Compiled resource	Lazarus Resources	binary
.ico	Icon (typically for a program)		ico
.gitignore	Ignore list of git		text

Subversion or Git

These files would normally be stored in a repository as an adequate description of a project:

*.lpi
*.lpr
*.lfm
*.pas
*.pp

These files might contain manually-generated or imported information, or might be regenerated by the IDE or build process. In general, if they have the same basename as the project or a form or unit they're IDE-generated, but in all cases should be reviewed individually:

*.inc
*.res
*.lrs
*.rc
*.ico

These files are regenerated by the IDE or by a build so do not need to be stored:

*.ppu
*.o
*.a
*.lps
*.or
*.rst
*.compiled

Note that *.lrj files are generated for every form while tracking i18n, loss of these files can cause missing translations.

There is an example .gitignore file at [3].

Delphi

Project files

*.dfm
   Delphi form module
*.dof
   Delphi project options file
*.dsk
   Desktop configuration

Converting Delphi projects

Lazarus can convert at least some Delphi project files into its own format.

Application

General

*.txt
   Text file
*.po
   Gettext Portable Object
*.bak
   Backup
*.cfg
   Config file
*.chm
   Compiled Help File - contains html. See also package chm
*.csv
   Comma Separated Values text file format 
*.exe
   Directly executable program
*.hlp
   Help file
*.ini
   Initialization file
*.odt
   OpenDocument text document
*.pdf
   Portable Document Format
*.ps
   PostScript 
*.rtf
   Rich Text Format text file

Image

*.png
   Portable network graphic
*.bmp
   bitmap 
*.ico
   icon 
*.xpm
   pixmap 
*.ppm
   portable pixmap 
*.pgm
   portable graymap 
*.pbm
   portable bitmap 
*.jpg
   compressed image format standardised by the Joint Photographic Experts Group (JPEG)

XML

*.xml
*.dtd
*.xsd
*.xsl

Web

*.html
   Hypertext Markup Language
*.css
   Cascading style sheet

Archive

*.tar
   tape archive
*.zip
   a single file containing one or more compressed files

Database

*.dbf
   Database file
*.mdx
   Multiple index file

Spreadsheet

*.ods
   OpenOffice.org Calc spreadsheet File Format
*.xls  
   Microsoft Excel File Format
*.xlsx  
   Microsoft Office Open XML Excel File Format 

Operating system

Linux and Unix (excluding Darwin)

*.so 
   Shared object library
*.sh
   Shell script
*.deb
   Debian Package
*.rpm
   Red Hat Package Manager

Mac (Darwin)

*.app
   Application bundle (a structured directory)
*.dmg
   Disk Image File 
*.dylib 
   Dynamic shared library
*.framework
   Framework (set of interfaces or subframeworks)
*.icns
   Icon resource file containing one or more images used for an application icon 
*.plist
   Property list file (storage for serialised objects)

Windows

*.bat
   Batch file. It's a text file that contains a sequence of commands for a computer operating system.
*.dll 
  dynamic-link library
*.exe
   Directly executable program

See also

Alphabetical list of file extensions