Delphi is one of the first graphic development environments with the help of which applications from visual components such as buttons, scroll bars, etc. can be put together on the screen. This empty frame is then filled with content using the underlying programming language so that the desired functionality results. The first version appeared in 1995 as Delphi 1. Currently (as of the end of 2017) the version Delphi 10.2 Tokyo is RAD Studio 10.2 (Rapid Application Development). Initially, the only target platform available was Windows; today, MacOS, IOS, Android and Linux server applications can also be created. Delphi was initially developed by Borland, later sold to CodeGear and is now further developed and sold by Embarcadero Technologies. A version of Object Pascal (Borland Pascal or Embarcadero Pascal) was and is largely used as the programming language. In newer versions, C # or C ++ can also be used for the entire project or in individual components. In addition to the development environment, the most significant expansion at the beginning was the tight embedding of databases, which, like the surface development, was carried out using a set of specific (predominantly) visual components. On the one hand, this made simple applications possible that managed without a program line of their own code, on the other hand, the algorithmic further processing of the determined data has been greatly facilitated. The name Delphi is said to have been derived indirectly from Oracle, with oracles being known from Delphi in antiquity.
Licensing
Delphi licenses were initially chargeable, later there were different versions. B. were available free of charge to private users. This distribution policy was repeatedly changed in the course of the sales of the system, so that it was often not entirely clear when which version was legally available and at what price. This situation will have contributed to the fact that numerous free development environments were created on the basis of Free Pascal. Lazarus may serve as an example, which runs on the common operating systems and is therefore quite common. Currently (as of the end of 2017) the basic version of Delphi 10.2 Tokyo is again available free of charge.
Delphi project
In Delphi, a project consists of a directory that contains administrative information as well as at least one program file (e.g. Project.dpr) and a unit (e.g. Unit1.pas) which usually describes a screen window (e.g. Form1) . Its properties are outsourced to a file that can hardly be edited by the user (e.g. Unit1.dfm), which makes the actual program file clearer. A simple window with a button that changes color when a button is clicked may serve as an example. The slightly shortened program file Unit3.pas for the window and a screenshot of the development environment are given below.
Object Pascal
With Object-Pascal as a basis, Delphi had a broad foundation from the start, especially in the training area, as the teachers were able to build on their knowledge of Turbo-Pascal. The very similar syntax made the switch easier, the built-in GUI images (Graphical User Interface) made the results more attractive and the database connection greatly broadened the range of possible applications. In particular, examples from the IuG area (computer science and society) were made available to schools.
Compared to Pascal, the version of Object-Pascal used in Delphi has been syntactically somewhat expanded, but particularly in terms of content. This was done in the usual way via libraries, to which corresponding visual components for network or cloud operations, access to operating system and other resources were assigned, as well as through possibilities for cooperative work. Other concepts have been retained. Delphi usually compiles to an executable file in the respective operating system. B. makes the distribution of the applications easy, and objects are always placed on the head, which facilitates advanced programming concepts. Unfortunately, the developers are also responsible for managing the heap themselves, for example for freeing up memory. Without automatic garbage collection, many projects become more complicated than expected. However, there are tools that provide this functionality.
Use and dissemination
The good starting conditions for Delphi due to the earlier spread of Pascal have apparently become more of a burden over time. The use of syntactically C-like languages such as Java in education has made languages with comparable syntax much more popular. In current programming language rankings, Delphi can therefore be found in the low single-digit percentage range – if at all. Even a very good development environment is no longer a unique selling point. B. Visual Studio, Eclipse or NetBeans offer similar functionalities. Although the dot notation in the OOP area is a bit above the elementary syntax in almost all languages, including Delphi,
unit Unit3;
interface
uses … // benutzte Bibliotheken
type tForm3 = class(TForm)
Button1: TButton; procedure Button1Click(Sender: TObject);
end;
var Form3: tForm3;
implementation
{$R *.dfm}
procedure TForm3.Button1Click(Sender: TObject);
begin
Color := clRED // nur diese Codezeile muss „per Hand“ eingegeben werden
end;
end.