When we think "design-pattern", we are typically referring to logical level design-patterns, such as those presented in the seminal books on design-patterns ([1], [2] for example). These logical-level patterns provide structural and behavioural solutions to common problems when developing object-oriented software. These patterns are considered logical because they are independent of the programming language - for example - you can apply the Composite or Decorator pattern in C++, C#, Java, Smalltalk, or any programming language that is object-oriented.

An implementation-pattern (or an idiom), is simply a pattern that exists at the physical level. Typically they will be specific to a particular programming language and may well take advantage of a construct or concept specific to that programming language. There are many well documented implementation-patterns that are used in C# for example:

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