Before the development of .NET, COM and DNA technologies were used for application development on Microsoft platforms. COM is Microsoft’s framework for developing and supporting program component objects. DNA is a framework that integrates Web applications with the n-tier model of development. It is used to develop cost-effective solutions that can meet the demands of the Internet, intranet, global e-commerce, and corporate computing.

1. Technologies prior to .NET
COM and DNA
Before the development of .NET, COM and DNA technologies were used for
application development on Microsoft platforms. COM is Microsoft’s framework for
developing and supporting program component objects. DNA is a framework that
integrates Web applications with the n-tier model of development. It is used to
develop cost-effective solutions that can meet the demands of the Internet, intranet,
global e-commerce, and corporate computing.
Note : Windows DNA is short for Windows Distributed interNet Applications
Architecture, a marketing name for a collection of Microsoft technologies that enable
the Windows platform and the Internet to work together. Some of the principal
technologies comprising DNA include ActiveX, Dynamic HTML (DHTML) and COM.
Windows DNA has been largely superseded by the Microsoft .NET Framework, and
Microsoft no longer uses the term.
Drawbacks of Pre .NET Technologies
Programmers mostly used Microsoft Visual Basic (VB) and Microsoft Visual C++
(VC++) for developing applications using the COM/DNA technologies. However, these
technologies and the programming languages had several drawbacks.
(Windows DNA is short for Windows Distributed interNet Applications Architecture,
a marketing name for a collection of Microsoft technologies that enable the Windows
platform and the Internet to work together. Some of the principal technologies
comprising DNA include ActiveX, Dynamic HTML (DHTML) and COM. Windows DNA
has been largely superseded by the Microsoft .NET Framework, and Microsoft no
longer uses the term.)
Limitations of VC++ in COM/DNA Applications
The other language used by programmers to work with COM and DNA applications
was VC++. However, VC++ is a complex language. It has too many data types.
Additionally, exchange of data between different layers was difficult because of data
type compatibility issues. To resolve such issues, developers had to be familiar with
various libraries, such as Software Development Kit (SDK), Microsoft Foundation
Class (MFC), Active Template Library (ATL), and COM.
Drawbacks of COM/DNA
Apart from the limitations resulting from VB and VC++, the COM/DNA technologies
had several other drawbacks. These drawbacks became apparent as these
technologies were extended into larger enterprise-level settings and as integration
with the Internet became necessary. Some such drawbacks of COM/DNA

2. technologies included difficulty in integrating Internet technologies, difficulty in
side-by-side execution of components, and deployment issues.
Difficulty in Integrating Internet Technologies
The growth of the Internet has lead to the need of a tool for developing
Internet-based technologies. To address this need, Microsoft developed ASP. However,
ASP was not meant for structured and object-oriented development. It was also
difficult to design, debug, and maintain ASP code.
The existing technologies lacked the ability to communicate with users through
HyperText Transfer Protocol (HTTP) and HyperText Markup Language (HTML).
Developers required a standard that could enable processes to communicate over the
Internet. However, COM and DNA did not provide any such standard.
Difficulty in Side-by-Side Execution of Components
With DNA, it is difficult to have side-by-side execution of components. In side-by-side
execution of components, different versions of a component can coexist and run
simultaneously on the same machine and within the same process.
When a new application is installed with DNA, it overwrites the existing version of
the shared component with a new version of the component. Usually, the new
version is not backward-compatible with the existing applications. Therefore, though
the new application works, existing applications that depend on the old version start
functioning incorrectly or stop functioning completely.
COM and Deployment
COM components are difficult to deploy. The COM standard was developed for use on
systems having limited memory and was designed with a focus on memory sharing
between applications. The Dynamic Link Libraries (DLLs) on such systems were
shared between applications to save memory.
Deployment Issues
The process of sharing DLLs between applications resulted in several deployment
issues. DLLs had to be registered in the local Windows Registry so that components
required to run an application could be located quickly. This resulted in other
limitations. For instance, you could not place a COM application on a CD-ROM or a
network drive and then run it from that location without an installation procedure.