Difference between Programming Paradigm, Design Pattern and Application Architecture?

I'm from a non-programming background and have often come across the terms like Programming Paradigm, Design Pattern and Application Architecture. Although I think I have a vague understanding of what these terms mean, I'd appreciate if someone could clarify what each is, how it is different开发者_开发知识库 from the other and how these concepts apply to Objective C.

Programming Paradigm: Something like "Functional Programming", "Procedural Programming", and "Object Oriented Programming". The programming paradigm and the languages that use them inform how the code gets written. For example, in Object Oriented programming the code is divided up into classes (sometimes a language feature, sometimes not (e.g. javascript)), and typically supports inheritance and some type of polymorphism. The programmer creates the classes, and then instances of the classes (i.e. the objects) to carry out the operation of the program. In functional languages, the state changes on the computer are very heavily controlled by the language itself. Functions are first class objects, although not all languages where functions are first class objects are functional programming language (this topic is one of good debate). Code written with a functional languages involves lots of nested functions, almost every step of the program is new function invocation. For procedural programming, C programs and bash scripting are good examples, you just say do step 1, do step 2, etc, without creating classes and whatnot.

Design Pattern: A design pattern is a useful abstraction that can be implemented in any language. It is a "pattern" for doing things. Like if you have a bunch of steps you want to implement, you might use the 'composite' and 'command' patterns so make your implementation more generic. Think of a pattern as an established template for solving a common coding task in a generic way.

Application Architecture: Takes into consideration how you build a system to do stuff. So, for a web application, the architecture might involve x number of gateways behind a load balancer, that asynchronously feed queues. Messages are picked up by y processes running on z machines, with 1 primary db and a backup slave. Application architecture involves choosing the platform, languages, frameworks used. This is different than software architecture, which speaks more to how to actually implement the program given the software stack.

Some quick definitions,

Application Architecture describes the overall architecture of the software. For instance a web-based programs typically use a layered architecture where functionality is divided to several layers, such as user interface (html generation, handling commands from users), business logic (rules how the functions of the software are executed) and database (for persistent data). In contrast, a data processing application could use a so-called pipes and filters architecture, where a piece of data passes through a pipeline where different modules act on the data.

Design Patterns are a much lower level tool, providing proven models on how to organize code to gain specific functionality while not compromising the overall structure. Easy examples might include a Singleton (how to guarantee the existence of a single instance of a code) or a Facade (how to provide a simple external view to a more complex system).

On the other hand paradigms are the other extreme, guiding the principles on how code is actually laid out, and they each require quite different mindsets to apply. For instance, procedural programming is mainly concerned about dividing the program logic into functions and bundling those functions into modules. Object-oriented programming aims to encapsulate the data and the operations that manipulate the data into objects. Functional programming emphasizes the use of functions instead of separate statements following one another, avoiding side-effects and state changes.

Objective-C is mostly an object-oriented extension to C, design patterns and architecture are not language-specific constructs.

• A programming paradigm is a fundamental style of computer programming.

• Software Design Pattern - are best practice solutions to common software design problem. There are many design patterns for common problems. To learn more about design patterns you can read some books from this list 5 Best Books for Learning Design Patterns

• Application Architecture - Applications Architecture is the science and art of ensuring the suite of applications being used by an organization to create the composite application is scalable, reliable, available and manageable.

I guess any of these terms would apply to all programming languages. Design patterns exists in all programming languages.

These are logical terms defined to create higher level of abstraction.

Hope this helps

Think of the vernacular interpretation of those terms (i.e., outside of the field computer science).

• Paradigms are all-encompassing views of computation that affect not only what kinds of things you can do, but even what kinds of thoughts you can have; functional programming is an example of a programming paradigm.
• Patterns are simply well-established programming tricks, codified in some semi-formal manner.
• Application architecture is a broad term describing how complex applications are organised.

Objective-C primarily adds elements of the OO paradigm to the imperative language, C. Patterns and architecture are largely orthogonal to the language.

Simple English words A paradigm is a way of thinking when programming, where first class concepts are used to organize the software. Ex oop use classes as first class citizens, functional or lambda calculus use functions and their compositions, aspect uses aspects of a system .... And so on. When thinking a solution the first thing that comes to your mind are the first class citizens. The objective is to organize the solution into software components.

A design pattern is a common successful use of software components.

An application architecture is a set of design patterns put together in order to realize use case scdnarios.

Paradigm: a style or approach to programming. For example, In OOP, we use the concept of objects, classes to overall program. These objects contain data & behaviours & we connect them logically to complete the task.

Design Patterns: tried or tested solution, moreover reusable solutions, to the problem we encounter while everyday programming. For example, if we approach OOP paradigm, there are no. of patterns to help us solve specific problem.