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   ► KB ► Programming ► Delphi Prism   Print This     
  From the July 2009 Issue of Prestwood eMag
 
Delphi Prism Comments (// or { ... } or (* ... *))
 
Posted 11 years ago on 12/14/2008
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KB101700

Languages Focus: Comments

Commenting code generally has three purposes: to document your code, for psuedo coding prior to coding, and to embed compiler directives. Most languages support both a single line comment and a multiple line comment. Some languages also use comments to give instructions to the compiler or interpreter.

Delphi Prism Comments

Commenting Code
Delphi uses // for a single line comment and both {} and (**) for multiple line comments. Although you can nest different types of multiple line comments, it is recommended that you don't.

Compiler Directives - $
A special comment. Delphi compiler directives are in the form of {$DIRECTIVE}. Of interest for comments is using the $IFDEF compiler directive to remark out code.

Syntax Example: 
//This is a single line comment.
 
{
Multiple line
comment.
}
 
(*
This too is a
multiple line comment.
*)
 
{$IFDEF TEMPOUT}
  //...code here
{$ENDIF}

Compiler Directives

In the $IFDEF example above, the TEMPOUT identifier is not defined, the $IFDEF evaluates to false and skips the code during compile. The code is never compiled.

Custom Compiler Directives

In addition to using the many built-in compiler directives, you can define your own. Here is a simple example. 

{$Define MYDEBUGMODE}
{$IfDef MYDEBUGMODE}
  MessageBox.Show("In debug mode.");
{$Else}
  MessageBox.Show("Out of debug mode.");
{$EndIf}
{$UnDef MYDEBUGMODE}
{$IfDef MYDEBUGMODE}
  MessageBox.Show("In debug mode.");
{$Else}
  MessageBox.Show("Out of debug mode.");
{$EndIf}

More Info

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Code 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.

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Linked Certification Question(s)

The following are practice certification questions with answers highlighted. These questions were prepared by Mike Prestwood and are intended to stress an important aspect of this KB post. All our practice questions are intended to prepare you generally for passing any certification test as well as prepare you for professional work.

Beginner

1 Beginner Level Question

Question #1: True or False?

In Prism, you can nest multiple line comments as in the following:

{
(*
comment here
*)
}
  
MessageBox.Show("Or, like this...");
(*
{
comment here
}
*)
Answer:
  • True
  • False
    		•

     KB Article #101700 Counter
    7914
    Since 12/14/2008

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