In computer science

Computer science

Computer science or computing science is the study of the theoretical foundations of information and computation and of practical techniques for their implementation and application in computer systems...

, a concern is a particular set of behaviors needed by a computer program

Computer program

A computer program is a sequence of instructions written to perform a specified task with a computer. A computer requires programs to function, typically executing the program's instructions in a central processor. The program has an executable form that the computer can use directly to execute...

, the conceptual sections. A concern can be as general as database

Database

A database is an organized collection of data for one or more purposes, usually in digital form. The data are typically organized to model relevant aspects of reality , in a way that supports processes requiring this information...

 interaction or as specific as performing a calculation, depending on the level of conversation between developers and the program being discussed. IBM uses the term concern space to describe this sectioning of concepts.

Usually these needs can be separated from each other into logical sections and allow the program to be modularized

Modularity (programming)

Modular programming is a software design technique that increases the extent to which software is composed of separate, interchangeable components called modules by breaking down program functions into modules, each of which accomplishes one function and contains everything necessary to accomplish...

. Edsger W. Dijkstra coined the term "separation of concerns

Separation of concerns

In computer science, separation of concerns is the process of separating a computer program into distinct features that overlap in functionality as little as possible. A concern is any piece of interest or focus in a program. Typically, concerns are synonymous with features or behaviors...

" to describe the mentality behind this modularization, which allows the programmer to reduce the complexity of the system being designed. Two different concerns that intermingle in the same section of code are called "highly coupled

Coupling (computer science)

In computer science, coupling or dependency is the degree to which each program module relies on each one of the other modules.Coupling is usually contrasted with cohesion. Low coupling often correlates with high cohesion, and vice versa...

". Sometimes the chosen module divisions do not allow for one concern to be completely separated from another, resulting in cross-cutting concern

Cross-cutting concern

In computer science, cross-cutting concerns are aspects of a program which affect other concerns.These concerns often cannot be cleanly decomposed from the rest of the system in both the design and implementation, and can result in either scattering , tangling , or both.For instance, if writing an...

s. The various programming paradigm

Programming paradigm

A programming paradigm is a fundamental style of computer programming. Paradigms differ in the concepts and abstractions used to represent the elements of a program and the steps that compose a computation A programming paradigm is a fundamental style of computer programming. (Compare with a...

s address the issue of cross-cutting concerns to different degrees. Data logging is a common cross-cutting concern, being used in many other parts of the program other than the particular module(s) that actually log the data. Since changes to the logging code can affect other sections, it could introduce bugs in the operation of the program.

Paradigms that specifically address the issue of concern separation:

• Object-oriented programming
  Object-oriented programming
  Object-oriented programming is a programming paradigm using "objects" – data structures consisting of data fields and methods together with their interactions – to design applications and computer programs. Programming techniques may include features such as data abstraction,...
  
  , describing concerns as objects
• Functional programming
  Functional programming
  In computer science, functional programming is a programming paradigm that treats computation as the evaluation of mathematical functions and avoids state and mutable data. It emphasizes the application of functions, in contrast to the imperative programming style, which emphasizes changes in state...
  
  , describing concerns as functions
• Aspect-oriented software development
  Aspect-oriented software development
  In computing, Aspect-oriented software development is an emerging software development technology that seeks new modularizations of software systems in order to isolate secondary or supporting functions from the main program's business logic...
  
  , treating concerns and their interaction as constructs of their own standing