From the February 2011 Issue of Prestwood eMag

Delphi Language Details: Pascal and PChar Strings By Mike Prestwood

Posted 21 years ago on 3/18/2003 and updated 12/12/2006 Take Away: Using Pascal and PChar strings in Delphi.  Tags: pchar , pascal , string , strings , delphi , object pascal KB100160

ObjectPascal has two varieties of string variables: Pascal strings and Pchar strings. PChar strings are also known as null terminated strings because the last character in memory is always the null character (ASCII 0).

Using Pascal strings

The first character in memory is used to store the length of the string. Because this character is an unsigned short integer it is limited to 255 characters; unsigned short integers have a range from 0 to 255.

procedure TForm1.Button3Click(Sender: TObject);

var

   sPascalType: String[20];

begin

   sPascalType := 'Felina Prestwood';

   ShowMessage(sPascalType);

end;

Using PChar strings

Here are some examples:

var

   s: String;

or

var

   s2: PChar;

for example, type in the following code.

procedure TForm1.Button4Click(Sender: TObject);

var

   s1: String;

   s2: PChar;

begin

   s1 := 'Felicia Prestwood';

   s2 := 'Felina Prestwood';

   ShowMessage(s1);

   ShowMessage(s2);

end;

lmsison

Comment 1 of 1 I've compiled my application in delphi 7. i received a warning that states Unsafe type 'PChar'.. what should i do? Posted 20 years ago

KB Post Contributed By Mike Prestwood:

Mike Prestwood is a drummer, an author, and creator of the PrestwoodBoards online community. He is the President & CEO of Prestwood IT Solutions. Prestwood IT provides Coding, Website, and Computer Tech services. Mike has authored 6 computer books and over 1,200 articles. As a drummer, he maintains play-drums.com and has authored 3 drum books. If you have a project you wish to discuss with Mike, you can send him a private message through his PrestwoodBoards home page or call him 9AM to 4PM PST at 916-726-5675 x205. Visit Profile