Title 1
In our previous lesson Registry as Delphi INI-File --
part 2, we
wrote this very basic example:
program ConsoleTest;
{$APPTYPE CONSOLE}
uses SysUtils;
begin
WriteLn('Program ConsoleTest is running.');
WriteLn('Press the ENTER key to stop');
ReadLn;
end.
Let's have a look at the meaning of the different keywords in the source code:
- program means that this unit as the program's main source unit, the .DPR
file. This keyword
is followed by the name of the project file, without the extension .DPR.
When you compile a project, Delphi uses the name of the project file for the name of
your EXE file
that it creates.
- $APPTYPE controls whether to generate a console application
or a graphical
UI application (UI = User Interface). Here, the {$APPTYPE CONSOLE}
directive tells
the compiler to generate a console application.
- uses is followed by a list of all the units that the unit ConsoleTest
uses, that is:
the other units that are part of the project.
We see that Delphi included the SysUtils unit. Also another unit is included,
the System unit,
but since System is included in every Delphi program, it's not necessary to
mention it in the uses directive.
- In between the keywords begin and end you add your code.
Note that the last end keyword is always followed by a dot character --
also called point,
period, or final stop. As you've probably guessed ;) this indicates the end
of the project
file.
Handling Input and Output
In a console application, you don't use VCL controls for input and output.
Communication with
the user is handled with Read and Write commands:
- WriteLn displays a message, followed by an end-of-line code that
positions the text cursor
at the beginning of the next line.
Example: display the line of text Program ConsoleTest is
running :
WriteLn('Program ConsoleTest is running');
- ReadLn inputs keystrokes, until the ENTER ("return") key
is pressed.
Example: read data until Enter is pressed and put in variable S:
ReadLn(S);
Example: simply wait until Enter is pressed:
ReadLn;
- Write displays data without an end-of-line.Thus, the ouput of the
next Write command
will appear directly after the displayed text.
Example: display 3 strings on the same line:
Write('one '); // note the space after the word
Write('two '); // note the space after the word
Write('three');
- Read to directly input data to one or more variables. The Read command
waits until the
number of data values that are typed (separated by spaces, if more than 1 value) is
equal to the
number of variables provided. Sounds complicated, doesn't it? That's why
Read isn't used
often, most input is done with ReadLn.
Example to input a single character to variable C, given that C is of type
"char" (press
ENTER afterwards) :
Read(C);
« Part 2: Registry as Delphi INI-File --
part 2
|
|