Delphi Source Files The compiler expects to find Delphi source code in files of three kinds:
Unit source files (which end with the .pas extension)
Project files (which end with the .dpr extension)
Package source files (which end with the .dpk extension)
Unit source files typically contain most of the code in an application. Each application has a single project file and
several unit files; the project file, which corresponds to the program file in traditional Pascal, organizes the unit files
into an application. Borland development tools automatically maintain a project file for each application.
If you are compiling a program from the command line, you can put all your source code into unit (.pas) files. If you
use the IDE to build your application, it will produce a project (.dpr) file.
Package source files are similar to project files, but they are used to construct special dynamically linkable libraries
called packages.
7
