Comparison of programming paradigms
Encyclopedia
This article attempts to set out the various similarities and differences between the various programming paradigm
s as a summary in both graphical and tabular format with links to the separate discussions concerning these similarities and differences in existing Wikipedia articles
None of the main programming paradigms have a precise, globally unanimous definition, let alone an official international standard. Nor is there any agreement on which paradigm constitutes the best approach to developing software. The subroutines that actually implement OOP methods
might be ultimately coded in an imperative, functional or procedural style that might, or might not, directly alter state
on behalf of the invoking program.
s existing in parallel (with sometimes apparently conflicting definitions), many of the underlying fundamental components
remain more or less the same (constant
s, variable
s, datafield
s, subroutine
s, Calls etc.) and must somehow therefore inevitably be incorporated into each separate paradigm with equally similar attributes or functions. The table above is not intended as a guide to precise similarities, but more an index of where to look for more information - based on the different naming of these entities - within each paradigm. Non-standardized implementations of each paradigm in numerous programming language
s further complicate the overall picture, especially those languages that support multiple paradigms
, each with its own jargon
.
is a term used to describe the "sweetening" of program functionality by the introduction of language features that facilitate particular usage, even if the end result could be achieved without them. One example of syntactic sugar may arguably be classes in C++
(as well as in Java
, C#, etc.). The C programming language is fully capable of object-oriented programming
using its facilities of function pointer
s, type casting, and structures. However, languages such as C++
aim to make object-oriented programming more convenient by introducing syntax specific to this coding style. Moreover, the specialized syntax works to emphasize the object-oriented approach. Similarly, functions and looping syntax in C
(as well as other procedural and structured programming languages) could be considered syntactic sugar. Assembly language
is fully capable of procedural or structured programming using its facilities for modifying register values and branching execution depending on program state. However, languages such as C introduced syntax specific to these coding styles to make procedural and structured programming more convenient. Features of the C# (C Sharp) programming language, such as properties and interfaces, similarly do not enable new functionality, but are designed to make good programming practices more prominent and more natural.
Some programmers feel that these features are either unimportant or outright frivolous. For example, Alan Perlis
once quipped, in a reference to bracket-delimited languages, that "syntactic sugar causes cancer of the semicolon
" (see Epigrams on Programming
).
An extension of this is the term "syntactic saccharin", meaning gratuitous syntax which does not actually make programming easier.
, a program coded in an imperative style, without using any subroutines at all, would have the lowest count. However, the binary
size of such a program might be larger than the same program coded using subroutines (as in functional and procedural programming) and would reference more "non-local"
physical instructions that may increase cache misses and increase instruction fetch overhead
in modern processors.
The paradigms that use subroutines extensively (including functional, procedural and object oriented) and do not also use significant inlining (via compiler optimization
s) will, consequently, use a greater percentage of total resources on the subroutine linkages themselves. Object oriented programs that do not deliberately alter program state
directly, instead using mutator method
s (or "setters") to encapsulate these state changes, will, as a direct consequence, have a greater overhead. This is due to the fact that message passing
is essentially a subroutine call, but with three more additional overheads: dynamic memory allocation, parameter copying and dynamic dispatch
). Obtaining memory from the heap and copying parameters for message passing may involve significant resources that far exceed those required for the state change itself. Accessors (or "getters") that merely return the values of private member variables also depend upon similar message passing subroutines, instead of using a more direct assignment (or comparison), adding to total path length.
), assuming no subroutine inlining, no macro preprocessors, register arithmetic and weighting each instruction 'step' as just 1 instruction - as a crude measure of instruction path length
- is presented below. The instruction step that is conceptually performing the actual state change is highlighted in bold typeface in each case. Note that the actual arithmetic operations used to compute the area of the circle are the same in all three paradigms, with the difference being that the procedural and object-oriented paradigms wrap those operations in a subroutine call that makes the computation general and reusable. The same effect could be achieved in a purely imperative program using a macro preprocessor at just the cost of increased program size (only at each macro invocation site) without a corresponding pro rata runtime cost (proportional to n invocations - that may be situated within an inner loop
for instance). Conversely, subroutine inlining by a compiler could reduce procedural programs to something similar in size to the purely imperative code. However, for object-oriented programs, even with inlining, messages still have to be built (from copies of the arguments) for processing by the object oriented methods. The overhead of calls, virtual or otherwise, is not dominated by the control flow
alteration itself - but by the surrounding calling convention
costs, like prologue and epilogue
code, stack setup and argument passing (see here for more realistic instruction path length, stack and other costs associated with calls on an x86 platform). See also here for a slide presentation by Eric S. Roberts ("The Allocation of Memory to Variables", chapter 7) - illustrating the use of stack and heap memory usage when summing three rational number
s in the Java
object oriented language.
The advantages of procedural abstraction and object-oriented-style polymorphism are not well illustrated by a small example like the one above. This example is designed principally to illustrate some intrinsic performance differences, not abstraction or code re-use.
(utilizing procedure calls with tail recursion) and concludes that "we should have a healthy respect for procedure calls" (because they are powerful) but suggested "use them sparingly"
In terms of the frequency of subroutine calls:-
on a variety of software, using an instruction-level profiling tool, measured how many instructions were required per dynamic storage allocation. The results showed that the lowest absolute number of instructions executed averaged around 50 but others reached as high as 611. See also "Heap:Pleasures and pains" by Murali R. Krishnan that states "Heap implementations tend to stay general for all platforms, and hence have heavy overhead". The above pseudocode example does not include a realistic estimate of this memory allocation pathlength or the memory prefix overheads involved and the subsequent associated garbage collection overheads (To gain some appreciation that heap allocation is not a "trivial" task, this is an example of one open source
microallocator by games developer, John W. Ratcliff
, consisting of nearly 1,000 lines of code).
, claim that "Heavy use of inheritance and dynamically-bound messages is likely to make code more extensible and reusable, but it also imposes a significant performance overhead, compared to an equivalent but non-extensible program written in a non-object-oriented manner. In some domains, such as structured graphics packages, the performance cost of the extra flexibility provided by using a heavily object-oriented style is acceptable. However, in other domains, such as basic data structure libraries, numerical computing packages, rendering libraries, and trace-driven simulation frameworks, the cost of message passing can be too great, forcing the programmer to avoid object-oriented programming in the “hot spots” of their application."
imposes quite considerable overheads when passing object
s from one system to another, especially when the transfer is in human-readable formats such as XML
and JSON
. This contrasts with compact binary formats for non object oriented data. Both encoding and decoding of the objects data value and its attributes are involved in the serialization process (that also includes awareness of complex issues such as inheritance, encapsulation and data hiding).
in March 2011 wrote: "This semester Dan Licata and I are co-teaching a new course on functional programming
for first-year prospective CS majors... Object-oriented programming is eliminated entirely from the introductory curriculum, because it is both anti-modular and anti-parallel by its very nature, and hence unsuitable for a modern CS curriculum. A proposed new course on object-oriented design methodology will be offered at the sophomore level for those students who wish to study this topic."
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 as a summary in both graphical and tabular format with links to the separate discussions concerning these similarities and differences in existing Wikipedia articles
Main paradigm approaches
The following are considered the main programming paradigms. There is inevitably some overlap in these non mutually-exclusive paradigms but the main features or identifiable differences are summarized in the following table:- Imperative programmingImperative programmingIn computer science, imperative programming is a programming paradigm that describes computation in terms of statements that change a program state...
- describes computation in terms of statementStatement (programming)In computer programming a statement can be thought of as the smallest standalone element of an imperative programming language. A program written in such a language is formed by a sequence of one or more statements. A statement will have internal components .Many languages In computer programming...
s that change a program stateState (computer science)In computer science and automata theory, a state is a unique configuration of information in a program or machine. It is a concept that occasionally extends into some forms of systems programming such as lexers and parsers.... - Functional programmingFunctional programmingIn 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...
- treats computationComputationComputation is defined as any type of calculation. Also defined as use of computer technology in Information processing.Computation is a process following a well-defined model understood and expressed in an algorithm, protocol, network topology, etc...
as the evaluation of mathematical functionFunction (mathematics)In mathematics, a function associates one quantity, the argument of the function, also known as the input, with another quantity, the value of the function, also known as the output. A function assigns exactly one output to each input. The argument and the value may be real numbers, but they can...
s and avoids stateProgram stateOne of the key concepts in computer programming is the idea of state, essentially a snapshot of the measure of various conditions in the system. Most programming languages require a considerable amount of state information in order to operate properly - information which is generally hidden from...
and mutableImmutable objectIn object-oriented and functional programming, an immutable object is an object whose state cannot be modified after it is created. This is in contrast to a mutable object, which can be modified after it is created...
data. - Procedural programmingProcedural programmingProcedural programming can sometimes be used as a synonym for imperative programming , but can also refer to a programming paradigm, derived from structured programming, based upon the concept of the procedure call...
/ structured programmingStructured programmingStructured programming is a programming paradigm aimed on improving the clarity, quality, and development time of a computer program by making extensive use of subroutines, block structures and for and while loops - in contrast to using simple tests and jumps such as the goto statement which could...
- specifying the steps the program must take to reach the desired state - Event-driven programmingEvent-driven programmingIn computer programming, event-driven programming or event-based programming is a programming paradigm in which the flow of the program is determined by events—i.e., sensor outputs or user actions or messages from other programs or threads.Event-driven programming can also be defined as an...
- the flow of the program is determined by eventEvent (computing)In computing an event is an action that is usually initiated outside the scope of a program and that is handled by a piece of code inside the program. Typically events are handled synchronous with the program flow, that is, the program has one or more dedicated places where events are handled...
s—i.e., sensorSensorA sensor is a device that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument. For example, a mercury-in-glass thermometer converts the measured temperature into expansion and contraction of a liquid which can be read on a calibrated...
outputs or user actions (mouse clicks, key presses) or messagesMessage passingMessage passing in computer science is a form of communication used in parallel computing, object-oriented programming, and interprocess communication. In this model, processes or objects can send and receive messages to other processes...
from other programs or threadsThread (computer science)In computer science, a thread of execution is the smallest unit of processing that can be scheduled by an operating system. The implementation of threads and processes differs from one operating system to another, but in most cases, a thread is contained inside a process...
. - Object oriented programming (OOP) - uses "objectsObject (computer science)In computer science, an object is any entity that can be manipulated by the commands of a programming language, such as a value, variable, function, or data structure...
" – data structures consisting of datafieldsField (computer science)In computer science, data that has several parts can be divided into fields. Relational databases arrange data as sets of database records, also called rows. Each record consists of several fields; the fields of all records form the columns....
and methodsMethod (computer science)In object-oriented programming, a method is a subroutine associated with a class. Methods define the behavior to be exhibited by instances of the associated class at program run time...
together with their interactions – to design applications and computer programs. - Declarative programmingDeclarative programmingIn computer science, declarative programming is a programming paradigm that expresses the logic of a computation without describing its control flow. Many languages applying this style attempt to minimize or eliminate side effects by describing what the program should accomplish, rather than...
- expresses the logic of a computationComputationComputation is defined as any type of calculation. Also defined as use of computer technology in Information processing.Computation is a process following a well-defined model understood and expressed in an algorithm, protocol, network topology, etc...
without describing its control flowControl flowIn computer science, control flow refers to the order in which the individual statements, instructions, or function calls of an imperative or a declarative program are executed or evaluated.... - Automata-based programmingAutomata-Based ProgrammingAutomata-based programming is a programming paradigm in which the program or its part is thought of as a model of a finite state machine or any other formal automaton...
- in which the program or its part is thought of as a model of a finite state machine or any other formal automata.
None of the main programming paradigms have a precise, globally unanimous definition, let alone an official international standard. Nor is there any agreement on which paradigm constitutes the best approach to developing software. The subroutines that actually implement OOP methods
Method (computer science)
In object-oriented programming, a method is a subroutine associated with a class. Methods define the behavior to be exhibited by instances of the associated class at program run time...
might be ultimately coded in an imperative, functional or procedural style that might, or might not, directly alter state
State (computer science)
In computer science and automata theory, a state is a unique configuration of information in a program or machine. It is a concept that occasionally extends into some forms of systems programming such as lexers and parsers....
on behalf of the invoking program.
| 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... |
Description | Main characteristics (examples) | Related paradigm(s) | Critics? |
|---|---|---|---|---|
| Imperative Imperative programming In computer science, imperative programming is a programming paradigm that describes computation in terms of statements that change a program state... |
Computation in terms of statement Statement (programming) In computer programming a statement can be thought of as the smallest standalone element of an imperative programming language. A program written in such a language is formed by a sequence of one or more statements. A statement will have internal components .Many languages In computer programming... s that directly change a program state State (computer science) In computer science and automata theory, a state is a unique configuration of information in a program or machine. It is a concept that occasionally extends into some forms of systems programming such as lexers and parsers.... (datafields Field (computer science) In computer science, data that has several parts can be divided into fields. Relational databases arrange data as sets of database records, also called rows. Each record consists of several fields; the fields of all records form the columns.... ) |
Direct assignment Assignment (computer science) In computer programming, an assignment statement sets or re-sets the value stored in the storage location denoted by a variable name. In most imperative computer programming languages, assignment statements are one of the basic statements... s, Common data structure Data structure In computer science, a data structure is a particular way of storing and organizing data in a computer so that it can be used efficiently.Different kinds of data structures are suited to different kinds of applications, and some are highly specialized to specific tasks... s, Global variable Global variable In computer programming, a global variable is a variable that is accessible in every scope . Interaction mechanisms with global variables are called global environment mechanisms... s |
Edsger W. Dijkstra, Michael A. Jackson Michael A. Jackson Michael Anthony Jackson is a British computer scientist, and independent computing consultant in London, England. He is also part-time researcher at AT&T Research, Florham Park, NJ, U.S., and visiting research professor at the Open University in the UK.- Biography :Jackson was educated at Harrow... |
|
| Structured Structured programming Structured programming is a programming paradigm aimed on improving the clarity, quality, and development time of a computer program by making extensive use of subroutines, block structures and for and while loops - in contrast to using simple tests and jumps such as the goto statement which could... |
A style of Imperative programming Imperative programming In computer science, imperative programming is a programming paradigm that describes computation in terms of statements that change a program state... with more logical program structure |
Structograms, Indentation Indent style In computer programming, an indent style is a convention governing the indentation of blocks of code to convey the program's structure. This article largely addresses the C programming language and its descendants, but can be applied to most other programming languages... , absence of GOTO Goto goto is a statement found in many computer programming languages. It is a combination of the English words go and to. It performs a one-way transfer of control to another line of code; in contrast a function call normally returns control... statements |
Imperative Imperative programming In computer science, imperative programming is a programming paradigm that describes computation in terms of statements that change a program state... |
|
| Functional 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... |
Treats computation Computation Computation is defined as any type of calculation. Also defined as use of computer technology in Information processing.Computation is a process following a well-defined model understood and expressed in an algorithm, protocol, network topology, etc... as the evaluation of mathematical function Function (mathematics) In mathematics, a function associates one quantity, the argument of the function, also known as the input, with another quantity, the value of the function, also known as the output. A function assigns exactly one output to each input. The argument and the value may be real numbers, but they can... s avoiding state Program state One of the key concepts in computer programming is the idea of state, essentially a snapshot of the measure of various conditions in the system. Most programming languages require a considerable amount of state information in order to operate properly - information which is generally hidden from... and mutable Immutable object In object-oriented and functional programming, an immutable object is an object whose state cannot be modified after it is created. This is in contrast to a mutable object, which can be modified after it is created... data. |
Lambda calculus Lambda calculus In mathematical logic and computer science, lambda calculus, also written as λ-calculus, is a formal system for function definition, function application and recursion. The portion of lambda calculus relevant to computation is now called the untyped lambda calculus... , Compositionality, Formula Formula In mathematics, a formula is an entity constructed using the symbols and formation rules of a given logical language.... , Referential transparency, no side effects Side effect (computer science) In computer science, a function or expression is said to have a side effect if, in addition to returning a value, it also modifies some state or has an observable interaction with calling functions or the outside world... |
||
| Procedural Procedural programming Procedural programming can sometimes be used as a synonym for imperative programming , but can also refer to a programming paradigm, derived from structured programming, based upon the concept of the procedure call... |
Derived from structured programming Structured programming Structured programming is a programming paradigm aimed on improving the clarity, quality, and development time of a computer program by making extensive use of subroutines, block structures and for and while loops - in contrast to using simple tests and jumps such as the goto statement which could... , based upon the concept of modular programming Modular 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... or the procedure call |
Local variable Local variable In computer science, a local variable is a variable that is given local scope. Such a variable is accessible only from the function or block in which it is declared. In programming languages with only two levels of visibility, local variables are contrasted with global variables... s, sequence, selection, iteration Iteration Iteration means the act of repeating a process usually with the aim of approaching a desired goal or target or result. Each repetition of the process is also called an "iteration," and the results of one iteration are used as the starting point for the next iteration.-Mathematics:Iteration in... , and modularization Modular 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... |
Structured Structured programming Structured programming is a programming paradigm aimed on improving the clarity, quality, and development time of a computer program by making extensive use of subroutines, block structures and for and while loops - in contrast to using simple tests and jumps such as the goto statement which could... , Imperative Imperative programming In computer science, imperative programming is a programming paradigm that describes computation in terms of statements that change a program state... |
|
| Event-driven Event-driven programming In computer programming, event-driven programming or event-based programming is a programming paradigm in which the flow of the program is determined by events—i.e., sensor outputs or user actions or messages from other programs or threads.Event-driven programming can also be defined as an... including time driven Time-driven programming Time-driven programming is a computer programming paradigm, where the control flow of the computer program is driven by a clock and is often used in Real-time computing. A program is divided into a set of tasks , which has a periodic activation pattern... |
Program flow is mainly determined by event Event (computing) In computing an event is an action that is usually initiated outside the scope of a program and that is handled by a piece of code inside the program. Typically events are handled synchronous with the program flow, that is, the program has one or more dedicated places where events are handled... s (such as mouse clicks or interrupts including timer) |
Main loop, Event handlers, Asynchronous processes | Procedural Procedural programming Procedural programming can sometimes be used as a synonym for imperative programming , but can also refer to a programming paradigm, derived from structured programming, based upon the concept of the procedure call... |
|
| Object-oriented | Treats datafields Field (computer science) In computer science, data that has several parts can be divided into fields. Relational databases arrange data as sets of database records, also called rows. Each record consists of several fields; the fields of all records form the columns.... as "objects" manipulated only through pre-defined methods Method (computer science) In object-oriented programming, a method is a subroutine associated with a class. Methods define the behavior to be exhibited by instances of the associated class at program run time... |
Objects Object (computer science) In computer science, an object is any entity that can be manipulated by the commands of a programming language, such as a value, variable, function, or data structure... , Methods Method (computer science) In object-oriented programming, a method is a subroutine associated with a class. Methods define the behavior to be exhibited by instances of the associated class at program run time... , Message passing Message passing Message passing in computer science is a form of communication used in parallel computing, object-oriented programming, and interprocess communication. In this model, processes or objects can send and receive messages to other processes... , Information hiding Information hiding In computer science, information hiding is the principle of segregation of the design decisions in a computer program that are most likely to change, thus protecting other parts of the program from extensive modification if the design decision is changed... , Data abstraction, Encapsulation, Polymorphism Polymorphism in object-oriented programming Subtype polymorphism, almost universally called just polymorphism in the context of object-oriented programming, is the ability to create a variable, a function, or an object that has more than one form. The word derives from the Greek "πολυμορφισμός" meaning "having multiple forms"... , Inheritance Inheritance (computer science) In object-oriented programming , inheritance is a way to reuse code of existing objects, establish a subtype from an existing object, or both, depending upon programming language support... and Serialization/Marshalling Serialization In computer science, in the context of data storage and transmission, serialization is the process of converting a data structure or object state into a format that can be stored and "resurrected" later in the same or another computer environment... |
See here and | |
| Declarative Declarative programming In computer science, declarative programming is a programming paradigm that expresses the logic of a computation without describing its control flow. Many languages applying this style attempt to minimize or eliminate side effects by describing what the program should accomplish, rather than... |
Expresses the logic of a computation Computation Computation is defined as any type of calculation. Also defined as use of computer technology in Information processing.Computation is a process following a well-defined model understood and expressed in an algorithm, protocol, network topology, etc... without describing its detailed control flow Control flow In computer science, control flow refers to the order in which the individual statements, instructions, or function calls of an imperative or a declarative program are executed or evaluated.... |
(4GLs, Spreadsheet Spreadsheet A spreadsheet is a computer application that simulates a paper accounting worksheet. It displays multiple cells usually in a two-dimensional matrix or grid consisting of rows and columns. Each cell contains alphanumeric text, numeric values or formulas... s, Report program generators) |
||
| Automata-based programming Automata-Based Programming Automata-based programming is a programming paradigm in which the program or its part is thought of as a model of a finite state machine or any other formal automaton... |
The program is thought of as a model of a finite state machine Finite state machine A finite-state machine or finite-state automaton , or simply a state machine, is a mathematical model used to design computer programs and digital logic circuits. It is conceived as an abstract machine that can be in one of a finite number of states... or any other formal automata. |
State enumeration Enumeration In mathematics and theoretical computer science, the broadest and most abstract definition of an enumeration of a set is an exact listing of all of its elements . The restrictions imposed on the type of list used depend on the branch of mathematics and the context in which one is working... , Control variable, Changes in state State (computer science) In computer science and automata theory, a state is a unique configuration of information in a program or machine. It is a concept that occasionally extends into some forms of systems programming such as lexers and parsers.... , Isomorphism Isomorphism In abstract algebra, an isomorphism is a mapping between objects that shows a relationship between two properties or operations. If there exists an isomorphism between two structures, the two structures are said to be isomorphic. In a certain sense, isomorphic structures are... , State transition table State transition table In automata theory and sequential logic, a state transition table is a table showing what state a finite semiautomaton or finite state machine will move to, based on the current state and other inputs... |
Imperative Imperative programming In computer science, imperative programming is a programming paradigm that describes computation in terms of statements that change a program state... , Event-driven Event-driven programming In computer programming, event-driven programming or event-based programming is a programming paradigm in which the flow of the program is determined by events—i.e., sensor outputs or user actions or messages from other programs or threads.Event-driven programming can also be defined as an... |
|
| 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... |
Description | Main characteristics (examples) | Related paradigm(s) | Critics? |
Differences in terminology
Despite multiple (types of) programming paradigmParadigm
The word paradigm has been used in science to describe distinct concepts. It comes from Greek "παράδειγμα" , "pattern, example, sample" from the verb "παραδείκνυμι" , "exhibit, represent, expose" and that from "παρά" , "beside, beyond" + "δείκνυμι" , "to show, to point out".The original Greek...
s existing in parallel (with sometimes apparently conflicting definitions), many of the underlying fundamental components
Essence
In philosophy, essence is the attribute or set of attributes that make an object or substance what it fundamentally is, and which it has by necessity, and without which it loses its identity. Essence is contrasted with accident: a property that the object or substance has contingently, without...
remain more or less the same (constant
Constant (programming)
In computer programming, a constant is an identifier whose associated value cannot typically be altered by the program during its execution...
s, variable
Variable (programming)
In computer programming, a variable is a symbolic name given to some known or unknown quantity or information, for the purpose of allowing the name to be used independently of the information it represents...
s, datafield
Field (computer science)
In computer science, data that has several parts can be divided into fields. Relational databases arrange data as sets of database records, also called rows. Each record consists of several fields; the fields of all records form the columns....
s, subroutine
Subroutine
In computer science, a subroutine is a portion of code within a larger program that performs a specific task and is relatively independent of the remaining code....
s, Calls etc.) and must somehow therefore inevitably be incorporated into each separate paradigm with equally similar attributes or functions. The table above is not intended as a guide to precise similarities, but more an index of where to look for more information - based on the different naming of these entities - within each paradigm. Non-standardized implementations of each paradigm in numerous programming language
Programming language
A programming language is an artificial language designed to communicate instructions to a machine, particularly a computer. Programming languages can be used to create programs that control the behavior of a machine and/or to express algorithms precisely....
s further complicate the overall picture, especially those languages that support multiple paradigms
Multi-paradigm programming language
Programming languages can be grouped by the number and types of paradigms supported.-Paradigm summaries:A concise reference for the programming paradigms listed in this article....
, each with its own jargon
Jargon
Jargon is terminology which is especially defined in relationship to a specific activity, profession, group, or event. The philosophe Condillac observed in 1782 that "Every science requires a special language because every science has its own ideas." As a rationalist member of the Enlightenment he...
.
Language support
Syntactic sugarSyntactic sugar
Syntactic sugar is a computer science term that refers to syntax within a programming language that is designed to make things easier to read or to express....
is a term used to describe the "sweetening" of program functionality by the introduction of language features that facilitate particular usage, even if the end result could be achieved without them. One example of syntactic sugar may arguably be classes in C++
C++
C++ is a statically typed, free-form, multi-paradigm, compiled, general-purpose programming language. It is regarded as an intermediate-level language, as it comprises a combination of both high-level and low-level language features. It was developed by Bjarne Stroustrup starting in 1979 at Bell...
(as well as in Java
Java (programming language)
Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities...
, C#, etc.). The C programming language is fully capable of 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,...
using its facilities of function pointer
Function pointer
A function pointer is a type of pointer in C, C++, D, and other C-like programming languages, and Fortran 2003. When dereferenced, a function pointer can be used to invoke a function and pass it arguments just like a normal function...
s, type casting, and structures. However, languages such as C++
C++
C++ is a statically typed, free-form, multi-paradigm, compiled, general-purpose programming language. It is regarded as an intermediate-level language, as it comprises a combination of both high-level and low-level language features. It was developed by Bjarne Stroustrup starting in 1979 at Bell...
aim to make object-oriented programming more convenient by introducing syntax specific to this coding style. Moreover, the specialized syntax works to emphasize the object-oriented approach. Similarly, functions and looping syntax in C
C (programming language)
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
(as well as other procedural and structured programming languages) could be considered syntactic sugar. Assembly language
Assembly language
An assembly language is a low-level programming language for computers, microprocessors, microcontrollers, and other programmable devices. It implements a symbolic representation of the machine codes and other constants needed to program a given CPU architecture...
is fully capable of procedural or structured programming using its facilities for modifying register values and branching execution depending on program state. However, languages such as C introduced syntax specific to these coding styles to make procedural and structured programming more convenient. Features of the C# (C Sharp) programming language, such as properties and interfaces, similarly do not enable new functionality, but are designed to make good programming practices more prominent and more natural.
Some programmers feel that these features are either unimportant or outright frivolous. For example, Alan Perlis
Alan Perlis
Alan Jay Perlis was an American computer scientist known for his pioneering work in programming languages and the first recipient of the Turing Award.-Biography:...
once quipped, in a reference to bracket-delimited languages, that "syntactic sugar causes cancer of the semicolon
Semicolon
The semicolon is a punctuation mark with several uses. The Italian printer Aldus Manutius the Elder established the practice of using the semicolon to separate words of opposed meaning and to indicate interdependent statements. "The first printed semicolon was the work of ... Aldus Manutius"...
" (see Epigrams on Programming
Epigrams on Programming
Epigrams on Programming is an article by Alan Perlis published in 1982, for ACM's SIGPLAN journal. They are a series of short, programming language neutral, humorous statements about computers and programming, which are widely quoted....
).
An extension of this is the term "syntactic saccharin", meaning gratuitous syntax which does not actually make programming easier.
Performance comparison
Purely in terms of total instruction path lengthInstruction path length
In computer performance, the instruction path length is the number of machine code instructions required to execute a section of a computer program. The total path length for the entire program could be deemed a measure of the algorithm's performance on a particular computer hardware...
, a program coded in an imperative style, without using any subroutines at all, would have the lowest count. However, the binary
Binary file
A binary file is a computer file which may contain any type of data, encoded in binary form for computer storage and processing purposes; for example, computer document files containing formatted text...
size of such a program might be larger than the same program coded using subroutines (as in functional and procedural programming) and would reference more "non-local"
Locality of reference
In computer science, locality of reference, also known as the principle of locality, is the phenomenon of the same value or related storage locations being frequently accessed. There are two basic types of reference locality. Temporal locality refers to the reuse of specific data and/or resources...
physical instructions that may increase cache misses and increase instruction fetch overhead
Computational overhead
In computer science, overhead is generally considered any combination of excess or indirect computation time, memory, bandwidth, or other resources that are required to attain a particular goal...
in modern processors.
The paradigms that use subroutines extensively (including functional, procedural and object oriented) and do not also use significant inlining (via compiler optimization
Compiler optimization
Compiler optimization is the process of tuning the output of a compiler to minimize or maximize some attributes of an executable computer program. The most common requirement is to minimize the time taken to execute a program; a less common one is to minimize the amount of memory occupied...
s) will, consequently, use a greater percentage of total resources on the subroutine linkages themselves. Object oriented programs that do not deliberately alter program state
Program state
One of the key concepts in computer programming is the idea of state, essentially a snapshot of the measure of various conditions in the system. Most programming languages require a considerable amount of state information in order to operate properly - information which is generally hidden from...
directly, instead using mutator method
Mutator method
In computer science, a mutator method is a method used to control changes to a variable.The mutator method, sometimes called a "setter", is most often used in object-oriented programming, in keeping with the principle of encapsulation...
s (or "setters") to encapsulate these state changes, will, as a direct consequence, have a greater overhead. This is due to the fact that message passing
Message passing
Message passing in computer science is a form of communication used in parallel computing, object-oriented programming, and interprocess communication. In this model, processes or objects can send and receive messages to other processes...
is essentially a subroutine call, but with three more additional overheads: dynamic memory allocation, parameter copying and dynamic dispatch
Dynamic dispatch
In computer science, dynamic dispatch is the process of mapping a message to a specific sequence of code at runtime. This is done to support the cases where the appropriate method can't be determined at compile-time...
). Obtaining memory from the heap and copying parameters for message passing may involve significant resources that far exceed those required for the state change itself. Accessors (or "getters") that merely return the values of private member variables also depend upon similar message passing subroutines, instead of using a more direct assignment (or comparison), adding to total path length.
Pseudocode examples comparing various paradigms
A pseudocode comparison of imperative, procedural, and object oriented approaches used to calculate the area of a circle (), assuming no subroutine inlining, no macro preprocessors, register arithmetic and weighting each instruction 'step' as just 1 instruction - as a crude measure of instruction path lengthInstruction path length
In computer performance, the instruction path length is the number of machine code instructions required to execute a section of a computer program. The total path length for the entire program could be deemed a measure of the algorithm's performance on a particular computer hardware...
- is presented below. The instruction step that is conceptually performing the actual state change is highlighted in bold typeface in each case. Note that the actual arithmetic operations used to compute the area of the circle are the same in all three paradigms, with the difference being that the procedural and object-oriented paradigms wrap those operations in a subroutine call that makes the computation general and reusable. The same effect could be achieved in a purely imperative program using a macro preprocessor at just the cost of increased program size (only at each macro invocation site) without a corresponding pro rata runtime cost (proportional to n invocations - that may be situated within an inner loop
Inner loop
In computer programs, an important form of control flow is the loop. For example, this small pseudo-code program uses two nested loops to iterate over all the entries of an n×n matrix, changing their values so that the matrix becomes an identity matrix: for a in 1..n for b in 1..n ...
for instance). Conversely, subroutine inlining by a compiler could reduce procedural programs to something similar in size to the purely imperative code. However, for object-oriented programs, even with inlining, messages still have to be built (from copies of the arguments) for processing by the object oriented methods. The overhead of calls, virtual or otherwise, is not dominated by the control flow
Control flow
In computer science, control flow refers to the order in which the individual statements, instructions, or function calls of an imperative or a declarative program are executed or evaluated....
alteration itself - but by the surrounding calling convention
Calling convention
In computer science, a calling convention is a scheme for how subroutines receive parameters from their caller and how they return a result; calling conventions can differ in:...
costs, like prologue and epilogue
Function prologue
In assembly language programming, the function prologue is a few lines of code at the beginning of a function, which prepare the stack and registers for use within the function...
code, stack setup and argument passing (see here for more realistic instruction path length, stack and other costs associated with calls on an x86 platform). See also here for a slide presentation by Eric S. Roberts ("The Allocation of Memory to Variables", chapter 7) - illustrating the use of stack and heap memory usage when summing three rational number
Rational number
In mathematics, a rational number is any number that can be expressed as the quotient or fraction a/b of two integers, with the denominator b not equal to zero. Since b may be equal to 1, every integer is a rational number...
s in the Java
Java (programming language)
Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities...
object oriented language.
| Imperative | Procedural | Object-oriented |
|---|---|---|
|
|
|
The advantages of procedural abstraction and object-oriented-style polymorphism are not well illustrated by a small example like the one above. This example is designed principally to illustrate some intrinsic performance differences, not abstraction or code re-use.
Subroutine/Method call overhead
The presence of a (called) subroutine in a program contributes nothing extra to the functionality of the program regardless of paradigm, but may contribute greatly to the structuring and generality of the program, making it much easier to write, modify, and extend. The extent to which different paradigms utilize subroutines (and their consequent memory requirements) influences the overall performance of the complete algorithm, although as Guy Steele pointed out in a 1977 paper, a well-designed programming language implementation can have very low overheads for procedural abstraction (but laments, in most implementations, that they seldom achieve this in practice - being "rather thoughtless or careless in this regard"). In the same paper, Steele also makes a considered case for automata-based programmingAutomata-Based Programming
Automata-based programming is a programming paradigm in which the program or its part is thought of as a model of a finite state machine or any other formal automaton...
(utilizing procedure calls with tail recursion) and concludes that "we should have a healthy respect for procedure calls" (because they are powerful) but suggested "use them sparingly"
In terms of the frequency of subroutine calls:-
- for procedural programming, the granularity of the code is largely determined by the number of discrete procedures or moduleModular programmingModular 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...
s. - for functional programming, frequent calls to library subroutines are commonplace (but may be frequently inlined by the optimizing compiler)
- for object oriented programming, the number of method calls invoked is also partly determined by the granularity of the data structures and may therefore include many "read-only" accesses to low level objects that are encapsulated (and therefore accessible in no other, more direct, way). Since increased granularity is a prerequisite for greater code reuseCode reuseCode reuse, also called software reuse, is the use of existing software, or software knowledge, to build new software.-Overview:Ad hoc code reuse has been practiced from the earliest days of programming. Programmers have always reused sections of code, templates, functions, and procedures...
, the tendency is towards fine-grained data structures, and a corresponding increase in the number of discrete objects (and their methods) and, consequently, subroutine calls. The creation of "god objectGod objectIn object-oriented programming, a God object is an object that knows too much or does too much. The God object is an example of an anti-pattern....
s" is actively discouraged. Constructors also add to the count as they are also subroutine calls (unless they are inlined). Performance problems caused by excessive granularity may not become apparent until scalabilityScalabilityIn electronics scalability is the ability of a system, network, or process, to handle growing amount of work in a graceful manner or its ability to be enlarged to accommodate that growth...
becomes an issue. - for other paradigms, where a mixture of the above paradigms may be employed, subroutine usage is less predictable.
Allocation of dynamic memory for Message storage and object storage
Uniquely, the object oriented paradigm involves dynamic allocation of memory from heap storage for both object creation and message passing. A 1994 benchmark - "Memory Allocation Costs in Large C and C++ Programs" conducted by Digital Equipment CorporationDigital Equipment Corporation
Digital Equipment Corporation was a major American company in the computer industry and a leading vendor of computer systems, software and peripherals from the 1960s to the 1990s...
on a variety of software, using an instruction-level profiling tool, measured how many instructions were required per dynamic storage allocation. The results showed that the lowest absolute number of instructions executed averaged around 50 but others reached as high as 611. See also "Heap:Pleasures and pains" by Murali R. Krishnan that states "Heap implementations tend to stay general for all platforms, and hence have heavy overhead". The above pseudocode example does not include a realistic estimate of this memory allocation pathlength or the memory prefix overheads involved and the subsequent associated garbage collection overheads (To gain some appreciation that heap allocation is not a "trivial" task, this is an example of one open source
Open source
The term open source describes practices in production and development that promote access to the end product's source materials. Some consider open source a philosophy, others consider it a pragmatic methodology...
microallocator by games developer, John W. Ratcliff
John W. Ratcliff
John W. Ratcliff is a noted game developer, best known for creating the bestselling games 688 Attack Sub and SSN-21 Seawolf. -Biography:...
, consisting of nearly 1,000 lines of code).
Dynamically dispatched Message calls v. Direct procedure Call overheads
In their Abstract "Optimization of Object-Oriented Programs Using Static Class Hierarchy Analysis", Jeffrey Dean, David Grove, and Craig Chambers of the Department of Computer Science and Engineering, at the University of WashingtonUniversity of Washington
University of Washington is a public research university, founded in 1861 in Seattle, Washington, United States. The UW is the largest university in the Northwest and the oldest public university on the West Coast. The university has three campuses, with its largest campus in the University...
, claim that "Heavy use of inheritance and dynamically-bound messages is likely to make code more extensible and reusable, but it also imposes a significant performance overhead, compared to an equivalent but non-extensible program written in a non-object-oriented manner. In some domains, such as structured graphics packages, the performance cost of the extra flexibility provided by using a heavily object-oriented style is acceptable. However, in other domains, such as basic data structure libraries, numerical computing packages, rendering libraries, and trace-driven simulation frameworks, the cost of message passing can be too great, forcing the programmer to avoid object-oriented programming in the “hot spots” of their application."
Serialization of objects
SerializationSerialization
In computer science, in the context of data storage and transmission, serialization is the process of converting a data structure or object state into a format that can be stored and "resurrected" later in the same or another computer environment...
imposes quite considerable overheads when passing object
Object (computer science)
In computer science, an object is any entity that can be manipulated by the commands of a programming language, such as a value, variable, function, or data structure...
s from one system to another, especially when the transfer is in human-readable formats such as XML
XML
Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....
and JSON
JSON
JSON , or JavaScript Object Notation, is a lightweight text-based open standard designed for human-readable data interchange. It is derived from the JavaScript scripting language for representing simple data structures and associative arrays, called objects...
. This contrasts with compact binary formats for non object oriented data. Both encoding and decoding of the objects data value and its attributes are involved in the serialization process (that also includes awareness of complex issues such as inheritance, encapsulation and data hiding).
Parallel computing
Carnegie-Mellon University Professor Robert HarperRobert Harper (computer scientist)
Robert "Bob" William Harper, Jr. is a computer science professor at Carnegie Mellon University who works in programming language research. He made major contributions to the design of the Standard ML programming language and the LF logical framework....
in March 2011 wrote: "This semester Dan Licata and I are co-teaching a new course on 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...
for first-year prospective CS majors... Object-oriented programming is eliminated entirely from the introductory curriculum, because it is both anti-modular and anti-parallel by its very nature, and hence unsuitable for a modern CS curriculum. A proposed new course on object-oriented design methodology will be offered at the sophomore level for those students who wish to study this topic."
See also
- Comparison of programming languagesComparison of programming languagesProgramming languages are used for controlling the behavior of a machine . Like natural languages, programming languages conform to rules for syntax and semantics.There are thousands of programming languages and new ones are created every year...
- Comparison of programming languages (basic instructions)Comparison of programming languages (basic instructions)Comparison of programming languages is a common topic of discussion among software engineers. Basic instructions of several programming languages are compared here.- Conventions of this article :...
- Granularity
- Message passingMessage passingMessage passing in computer science is a form of communication used in parallel computing, object-oriented programming, and interprocess communication. In this model, processes or objects can send and receive messages to other processes...
- SubroutineSubroutineIn computer science, a subroutine is a portion of code within a larger program that performs a specific task and is relatively independent of the remaining code....
Further reading
- "A Memory Allocator" by Doug Lea
- "Dynamic Memory Allocation and Linked Data Structures" by (Scottish Qualifications AuthorityScottish Qualifications AuthorityThe Scottish Qualifications Authority is a non-departmental public body responsible for accreditation and awarding. It is partly funded by the Education and Lifelong Learning Directorate of the Scottish Government, employing 750 staff, based in Glasgow and Dalkeith...
) - "Inside A Storage Allocator" by Dr. Newcomer Ph.D
External links
- Comparing Programming Paradigms by Dr Rachel Harrison and Mr Lins Samaraweera
- Comparing Programming Paradigms: an Evaluation of Functional and Object-Oriented Programs by Harrison, R., Samaraweera, L. G., Dobie, M. R. and Lewis, P. H. (1996) pp. 247–254. ISSN 0268-6961
- "The principal programming paradigms" By Peter Van Roy
- "Concepts, Techniques, and Models of Computer Programming" (2004) by Peter Van Roy & Seif Haridi, ISBN 0-262-22069-5
- The True Cost of Calls - from "Harder, Better, Faster, Stronger" blog by computer scientist Steven Pigeon