0. DISCLAIMER:
1. What is the registry?
2. What does the registry look like?
3. How to read and write data to the registry
    3.1 RegCreateKey()
    3.2 RegOpenKey()
    3.3 RegSetValue()
    3.4 RegQueryValue()
    3.5 RegDeleteKey()
    3.6 RegEnumKey()
4. An Example
5. Win95 features
6. REGDLL.DLL

The source code corresponding to this article is available for download as
registry.zip.

0. DISCLAIMER:

This article reflects my personal experiences with the registry and Delphi.
I had no 'real' documentation on this, except what shipped with Delphi. I
will not take any responsibility that occurs from the usage of the
procedures described in this article. The same applies to the usage of the
accompanying REGDLL.DLL and its interface. USE AT YOUR OWN RISK.

Suggestions and Comments are welcome. Please send them to:
Christian.Feichtner@jk.uni-linz.ac.at.

This article describes how to use the registry-database as an 'INI file'.
Especially with the advent of Windows 95 every 'good' windows application
should use the registry database to store its information.

Note that the described API routines are from the 16bit API. They work well
with the registry of Windows 95, but are not capable of using the special
new features of Windows 95.

1. What is the registry?

The registry is a heirarchical database, which is used to store information
for the whole system. OLE-apps made frequent use of the registry in Win31.
In Windows 95 the registry has grown to more than that. It not only stores
system information but has become a total replacement for the old-style INI
files. The INI files are only supported to maintain compatibility for 'old'
16bit Apps.

2. What does the registry look like?

As mentioned above, the registry is a heirarchical database. It is
organized as a tree. The most interesting key (and the only one accessable
from Delphi with the 16bit version) is the HKEY_CLASSES_ROOT.

This key can be used to store application settings. (Thus, I think there is
another key for Windows 95 apps. Since Delphi can only access this key, you
can use it until Delphi-32 becomes avaliable).

Example:

+ HKEY_CLASSES_ROOT      This is what a key could look like. Assume an
|                        application named Information Manager (which I'm
+--+-.IFM                currently developing) which saves its files with the
    |                     extension .IFM. Under Win95 the shell, open, command
    +--+-shell            and ShellNew keys are of special interest. (Yes they
       |                  can be used with Delphi as well.)
       +--+-open
       | |
       | +---command
       |
       +-ShellNew

.IFM\shell\open\command defines the command to be executed when the user
double clicks on the file (or under Win95 hits the right mouse button and
selects open).

The keys alone won't do the job. Normally there are values assigned to the
keys. Under Win31 these can only be strings. Win95 defines a kind of binary
and a DWORD as well.

The shell\open\command normally has a value like:

The selected filename will be substituted for '%1' and passed along as a
command-line parameter to the application. Your Delphi app can use
PARAMSTR(x) to get the x-th command line parameter. x=0 returns the full
path and name of the application itself.

If you are using the preview of Win95 and want your application to have an
entry in the 'New' popup menu (something like 'Information Manager 1.0
file'), you have to do the following:

Add a new (text) value for the ShellNew key, named NullFile, with a value
of "". Also name the extension (.IFM) equal to the entry of your app in the
registry. If the application has an entry named 'InfoMan', then name .IFM
as InfoMan.

Example:

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