An assembly can be a single file or it may consist of the multiple files. In case of multi-file, there is one master module containing the manifest while other assemblies exist as non-manifest modules. A module in .NET is a sub part of a multi-file .NET assembly

The .NET assembly is the standard for components developed with the Microsoft.NET. Dot NET assemblies may or may not be executable, i.e., they might exist as the executable (.exe) file or dynamic link library (DLL) file. All the .NET assemblies contain the definition of types, versioning information for the type, meta-data, and manifest. The designers of .NET have worked a lot on the component (assembly) resolution.

design pattern is a widely accepted solution to a recurring design problem in OOP a design pattern describes how to structure classes to meet a given requirement provides a general blueprint to follow when implementing part of a program does not describe how to structure the entire application does not describe specific algorithms focuses on relationships between classes

design patterns: make you more productive help you write cleaner code Observer and Singleton are just two of the many available if you like design patterns, try these resources: GoF book -- Design Patterns: Elements of Reusable Object-oriented Software design pattern examples in Java, see Design Patterns in Java Reference and Example Site