The Wiert Corner – irregular stream of stuff

Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

  • My badges

  • Twitter Updates

  • My Flickr Stream

  • Pages

  • All categories

  • Enter your email address to subscribe to this blog and receive notifications of new posts by email.

    Join 4,226 other subscribers

delphi – What are the list of all possible values for DVCLAL? – Stack Overflow

Posted by jpluimers on 2020/11/17

From a while ago, from notes even longer ago – around 1994 on DVCLAL the Delphi VCL Access License code which is actually a checking logic for determining the SKU (stock keeping unit) or Delphi license: [WayBack] delphi – What are the list of all possible values for DVCLAL? – Stack Overflow

There is no official documentation on this, so here is something from my notes of 15+ years ago:

The DVCLAL is there to check which SKU of Delphi you are using and it varies per SKU.

There are only checks for the Professional (RPR) and Client/Server (RCS) SKUs:

procedure RCS;

procedure RPR;

If they fail, they call this method:

procedure ALV;
  raise Exception.CreateRes(@SNL);


  SNL = 'Application is not licensed to use this feature';

Depending on the feature matrix and Delphi version, various components call RPR and RCS in their Create constructors to guarantee a minimum SKU.

Underneath, these RPR and RCS functions call the function  GDAL . Their names are historic and got documented around Delphi 2007:

  • [WayBack] GDAL (Get Delphi Access License)
  • [WayBack] RPR will Restrict to PRofessional license and higher
  • [WayBack] RCS will Restrict to Client/Service license and higher

Historically you had these levels of Delphi editions that could be distinguished this way:

  1. Personal
  2. Professional
  3. Client/Server (or Enterprise)

This excludes Starter and Community (which are “just” Personal), Turbo (which was “just” Professional), Architect and Ultimate, which are “just” Client/Server with extra tools.

A few years ago, another answer got added to that question explaining more details:

I am just adding another answer to this question, for all the people who search the for actual DVCLAL (Delphi Visual Component Library Access License) values, as well as some other information for all people who are curious how stuff works.

1) Like Jeroen Wiert Pluimers said, if you want to check for “Professional or higher” or “Enterprise only” inside your Delphi application/library/package/component, you can use RPR (Require Professional) or RCS (“Require Client/Server”; Client/Server was the name for the Enterprise edition in early Delphi versions) respectively. If the requirement is not met, ALV (Access License Violation) will be called which will raise an Exception with the message defined in SysConst.SNL (S Not Licensed). In English:

Application is not licensed to use this feature

2) In case you want to check for one specific edition, you can use the output of the function GDAL (Get Delphi Access License), which is one of the following (AL1s array):

AL1s[0] = $FFFFFFF0; // Standard/Personal edition DVCLAL value
AL1s[1] = $FFFFEBF0; // Professional edition DVCLAL value
AL1s[2] = $00000000; // Enterprise/ClientServer edition DVCLAL value
AL1s[3] = $FFFFFFFF; // DVCLAL resource not existing

if the DVCLAL resource has an invalid value, GDAL will call ALVwhich will raise an Exception with message SysConst.SNL.

3) In case you want to check the DVCLAL value of a foreign EXE/DLL file (e.g. if you want to write a Resource Editor, decompiler etc), then you’ll have to query the DVCLAL resource directly.

There are only three official values:

Standard:      23 78 5D 23 B6 A5 F3 19 43 F3 40 02 26 D1 11 C7
Professional:  A2 8C DF 98 7B 3C 3A 79 26 71 3F 09 0F 2A 25 17
Enterprise:    26 3D 4F 38 C2 82 37 B8 F3 24 42 03 17 9B 3A 83

4) Just for fun: If you solve the formula 0 = (ROR(a,15) xor a) xor (ROR(b,10) xor b) xor (ROR(c,5) xor c) xor (AL1 xor AL2) you can define any DVCLAL value (tuple a, b, c, d) you want! (AL1 and AL2 are the values in the AL1s and AL2s arrays which describe the desired Delphi edition; ROR is rotate right through carry)

For example, here are alternative DVCLALs which work too:

Standard:      00 00 00 00 00 00 00 00 9B 70 0C 66 6B 8F F3 99
Professional:  00 00 00 00 00 00 00 00 9A DB 73 0F 6A 30 8C F0
Enterprise:    00 00 00 00 00 00 00 00 D8 B2 48 11 D8 B2 48 11

To validate a DVCLAL, you calculate

AL1 := DVCLAL[0] xor DVCLAL[1] xor DVCLAL[2] xor DVCLAL[3];
AL2 := ROR(DVCLAL[0],15) xor ROR(DVCLAL[1],10) xor ROR(DVCLAL[2],5) xor DVCLAL[3];

and look up AL1 and AL2 in the array AL1s and AL2s,

This way you can disguise the edition you have used a little.

5) In the meantime, an official documentation, at least for the functions GDALRPR and RCS, has been published.

6) Of course, everything works for C++ Builder, too.

In the mean time, new posts explaining bits of DVCLAL related resources (like PACKAGEINFO and CHARTABLE) and the TPF0 form/datamodule resource have appeared, of which this is a selection:


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: