Programmed Inquiry, Learning, or Teaching ( PILOT ) is a simple high-level programming language developed in the 1960s. Like its younger sibling LOGO , it was an early foray into the technology of computer-assisted instruction .
63-457: PILOT is an imperative language similar in structure to BASIC and FORTRAN in its basic layout and structure. Its keywords are single characters, T for "type" to print text, or A for "accept", to input values from the user. PILOT was developed by John Amsden Starkweather , a psychology professor at the University of California, San Francisco medical center. In 1962, he developed
126-444: A class is only a definition; no memory is allocated. When memory is allocated to a class, it's called an object . Object-oriented imperative languages developed by combining the need for classes and the need for safe functional programming . A function, in an object-oriented language, is assigned to a class. An assigned function is then referred to as a method , member function , or operation . Object-oriented programming
189-737: A Y following the command letter is processed only if the match flag is set. Statements with N are processed only if the flag is not set. Extensions to core PILOT include arrays and floating point numbers in Apple PILOT for the Apple II , and LOGO -inspired turtle graphics in Atari PILOT for Atari 8-bit computers . Between 1979 and 1983 the UK PILOT User Group was run by Alec Wood a teacher at Wirral Grammar School for Boys, Merseyside UK. Several machine code versions of
252-433: A consequence, no one parallel programming language maps well to all computation problems. Thus, it is more convenient to use a base sequential language and insert API calls to parallel execution models via a programming model. Such parallel programming models can be classified according to abstractions that reflect the hardware, such as shared memory , distributed memory with message passing , notions of place visible in
315-476: A different point in time inside a different unit of code. The communication between the units of code is not explicit. In contrast, languages in the declarative paradigm do not state the order in which to execute operations. Instead, they supply a number of available operations in the system, along with the conditions under which each is allowed to execute. The implementation of the language's execution model tracks which operations are free to execute and chooses
378-410: A form of imperative programming , structures programs as a human-centered web, as in a hypertext essay: documentation is integral to the program, and the program is structured following the logic of prose exposition, rather than compiler convenience. Symbolic techniques such as reflection , which allow the program to refer to itself, might also be considered as a programming paradigm. However, this
441-509: A major contributor. The statements were English-like and verbose. The goal was to design a language so managers could read the programs. However, the lack of structured statements hindered this goal. COBOL's development was tightly controlled, so dialects did not emerge to require ANSI standards. As a consequence, it was not changed for 15 years until 1974. The 1990s version did make consequential changes, like object-oriented programming . ALGOL (1960) stands for "ALGOrithmic Language." It had
504-576: A mini PILOT were produced for the microcomputers of the time and a school in Scotland developed an interactive foreign language tutorial where pupils guided footprints around a town asking and answering questions in German, French, etc. An article in the December 1979 of Computer Age covered an early implementation called Tiny Pilot and gave a complete machine code listing. Versions of PILOT overlaid on
567-635: A profound influence on programming language design. Emerging from a committee of European and American programming language experts, it used standard mathematical notation and had a readable structured design. Algol was first to define its syntax using the Backus–Naur form . This led to syntax-directed compilers. It added features like: Algol's direct descendants include Pascal , Modula-2 , Ada , Delphi and Oberon on one branch. On another branch there's C , C++ and Java . BASIC (1964) stands for "Beginner's All Purpose Symbolic Instruction Code." It
630-471: A program written in C++ , Object Pascal , or PHP can be purely procedural , purely object-oriented , or can contain aspects of both paradigms, or others. When using a language that supports multiple paradigms, the developer chooses which paradigm elements to use. But, this choice may not involve considering paradigms per se. The developer often uses the features of a language as the language provides them and to
693-426: A program's state . In much the same way that the imperative mood in natural languages expresses commands, an imperative program consists of commands for the computer to perform. Imperative programming focuses on describing how a program operates step by step, rather than on high-level descriptions of its expected results. The term is often used in contrast to declarative programming , which focuses on what
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#1732780409392756-520: A rapid growth in interest in object-oriented programming . These languages were imperative in style, but added features to support objects . The last two decades of the 20th century saw the development of many such languages. Smalltalk -80, originally conceived by Alan Kay in 1969, was released in 1980, by the Xerox Palo Alto Research Center ( PARC ). Drawing from concepts in another object-oriented language— Simula (which
819-408: A remark (or a comment) explaining the code that follows. The first match string (if any) that is a substring of the accept buffer is assigned to the special variable $ MATCH. The buffer characters left of the first match are assigned to $ LEFT, and the characters on the right are assigned to $ RIGHT. The match flag is set to 'yes' or 'no', depending on whether a match is made. Any statement that has
882-459: A sequence of stateless function evaluations. When programming computers or systems with many processors, in process-oriented programming , programs are treated as sets of concurrent processes that act on a logical shared data structures . Many programming paradigms are as well known for the techniques they forbid as for those they support . For instance, pure functional programming disallows side-effects , while structured programming disallows
945-597: A simple language for automating learning tests called Computest. Starting in 1968, he developed a follow-on project called PILOT, for various computers of the time such as the SDS 940 . A line of PILOT code contains (from left to right) the following syntax elements: A label can also be alone in a line, not followed by other code. The syntax for a label is an asterisk followed by an identifier (alphanumeric string with alphabetic initial character). The following commands are used in "core PILOT". Lines beginning with "R:" indicate
1008-492: A syntax that would likely fail IBM's compiler. The American National Standards Institute (ANSI) developed the first Fortran standard in 1966. In 1978, Fortran 77 became the standard until 1991. Fortran 90 supports: COBOL (1959) stands for "COmmon Business Oriented Language." Fortran manipulated symbols. It was soon realized that symbols did not need to be numbers, so strings were introduced. The US Department of Defense influenced COBOL's development, with Grace Hopper being
1071-681: Is a C++ header file for the STUDENT class in a simple school application: Here is a C++ source file for the STUDENT class in a simple school application: Here is a driver program for demonstration: Here is a makefile to compile everything: Programming paradigm A programming paradigm is a relatively high-level way to conceptualize and structure the implementation of a computer program . A programming language can be classified as supporting one or more paradigms. Paradigms are separated along and described by different dimensions of programming. Some paradigms are about implications of
1134-442: Is a form of structured programming . Since the 1960s, structured programming and modular programming in general have been promoted as techniques to improve the maintainability and overall quality of imperative programs. The concepts behind object-oriented programming attempt to extend this approach. Procedural programming could be considered a step toward declarative programming. A programmer can often tell, simply by looking at
1197-534: Is a function with the same name as the class name. It is executed when the calling operation executes the new statement. A module's other file is the source file . Here is a C++ source file for the GRADE class in a simple school application: Here is a C++ header file for the PERSON class in a simple school application: Here is a C++ source file for the PERSON class in a simple school application: Here
1260-550: Is a paradigm that describes programs able to manipulate formulas and program components as data. Programs can thus effectively modify themselves, and appear to "learn", making them suited for applications such as artificial intelligence , expert systems , natural-language processing and computer games. Languages that support this paradigm include Lisp and Prolog . Differentiable programming structures programs so that they can be differentiated throughout, usually via automatic differentiation . Literate programming , as
1323-399: Is a relatively small language -- making it easy to write compilers. Its growth mirrored the hardware growth in the 1980s. Its growth also was because it has the facilities of assembly language , but uses a high-level syntax . It added advanced features like: C allows the programmer to control in which region of memory data is to be stored. Global variables and static variables require
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#17327804093921386-400: Is classified as imperative and is sometimes called the second-generation programming language . In the 1960s, assembly languages were developed to support library COPY and quite sophisticated conditional macro generation and preprocessing abilities, CALL to subroutine , external variables and common sections (globals), enabling significant code re-use and isolation from hardware specifics via
1449-851: Is considered the world's first object-oriented programming language , developed in the 1960s)— Bjarne Stroustrup designed C++ , an object-oriented language based on C . Design of C++ began in 1979 and the first implementation was completed in 1983. In the late 1980s and 1990s, the notable imperative languages drawing on object-oriented concepts were Perl , released by Larry Wall in 1987; Python , released by Guido van Rossum in 1990; Visual Basic and Visual C++ (which included Microsoft Foundation Class Library (MFC) 2.0), released by Microsoft in 1991 and 1993 respectively; PHP , released by Rasmus Lerdorf in 1994; Java , by James Gosling ( Sun Microsystems ) in 1995, JavaScript , by Brendan Eich ( Netscape ), and Ruby , by Yukihiro "Matz" Matsumoto, both released in 1995. Microsoft's .NET Framework (2002)
1512-401: Is designed to execute machine code , which is native to the computer and is usually written in the imperative style, although low-level compilers and interpreters using other paradigms exist for some architectures such as lisp machines . From this low-level perspective, the program state is defined by the contents of memory, and the statements are instructions in the native machine language of
1575-602: Is executing operations on objects . Object-oriented languages support a syntax to model subset/superset relationships. In set theory , an element of a subset inherits all the attributes contained in the superset. For example, a student is a person. Therefore, the set of students is a subset of the set of persons. As a result, students inherit all the attributes common to all persons. Additionally, students have unique attributes that other persons don't have. Object-oriented languages model subset/superset relationships using inheritance . Object-oriented programming became
1638-493: Is imperative at its core, as are its main target languages, VB.NET and C# that run on it; however Microsoft's F# , a functional language, also runs on it. FORTRAN (1958) was unveiled as "The IBM Mathematical FORmula TRANslating system." It was designed for scientific calculations, without string handling facilities. Along with declarations , expressions , and statements , it supported: It succeeded because: However, non IBM vendors also wrote Fortran compilers, but with
1701-401: Is met. Otherwise, the statements are skipped and the execution sequence continues from the statement following them. Unconditional branching statements allow an execution sequence to be transferred to another part of a program. These include the jump (called goto in many languages), switch , and the subprogram, subroutine , or procedure call (which usually returns to the next statement after
1764-654: The BASIC interpreters of early microcomputers were not unknown in the late 1970s and early 1980s, and Byte Magazine at one point published a non- Turing complete derivative of PILOT known as Waduzitdo by Larry Kheriarty as a way of demonstrating what a computer was capable of. PETPILOT (PILOT for the Commodore PET) was the first non-Commodore language for the PET and was written in Microsoft BASIC which shipped with
1827-566: The execution model , such as allowing side effects , or whether the sequence of operations is defined by the execution model. Other paradigms are about the way code is organized, such as grouping into units that include both state and behavior. Yet others are about syntax and grammar . Some common programming paradigms include (shown in hierarchical relationship): Programming paradigms come from computer science research into existing practices of software development . The findings allow for describing and comparing programming practices and
1890-497: The goto construct. Partly for this reason, new paradigms are often regarded as doctrinaire or overly rigid by those accustomed to older ones. Yet, avoiding certain techniques can make it easier to understand program behavior, and to prove theorems about program correctness. Programming paradigms can also be compared with programming models , which allows invoking an execution model by using only an API. Programming models can also be classified into paradigms based on features of
1953-523: The Basic syntax was too simple for large programs. Recent dialects added structure and object-oriented extensions. Microsoft's Visual Basic is still widely used and produces a graphical user interface . C programming language (1973) got its name because the language BCPL was replaced with B , and AT&T Bell Labs called the next version "C." Its purpose was to write the UNIX operating system . C
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2016-533: The IEEE Standards for PILOT, it includes Atari-specific features such as control of Laserdisc and CDROM devices. A 2018 hobbyist implementation, psPILOT, based in part on the IEEE standard, was implemented using Microsoft's PowerShell scripting language. Imperative programming In computer science , imperative programming is a programming paradigm of software that uses statements that change
2079-745: The OOP paradigm versus the procedural paradigm. The need for every object to have associative methods leads some skeptics to associate OOP with software bloat ; an attempt to resolve this dilemma came through polymorphism . Although most OOP languages are third-generation, it is possible to create an object-oriented assembler language. High Level Assembly (HLA) is an example of this that fully supports advanced data types and object-oriented assembly language programming – despite its early origins. Thus, differing programming paradigms can be seen rather like motivational memes of their advocates, rather than necessarily representing progress from one level to
2142-548: The October 1987 issue of COMPUTE! magazine. In 1991 the Institute of Electrical and Electronics Engineers (IEEE) published a standard for Pilot as IEEE Std 1154-1991. It has since been withdrawn. A reference implementation based on this was implemented by Eric Raymond , and maintained—-reluctantly—-for the next 15 years. In 1990 eSTeem PILOT for Atari ST computers was developed and programmed by Tom Nielsen, EdD. Based on
2205-525: The PET, with a little assistance from Bill Gates. It was created in 1979 by Dave Gomberg and could run on a 4K PET (which was never shipped) and ran well on the 8K PETs that Commodore shipped. It was written in Larry Tessler's living room on PET serial number 2. 1983's Vanilla PILOT for the Commodore 64 added turtle graphics, as did Super Turtle PILOT which was published as a type-in listing in
2268-440: The assignment of the resulting value to memory. Looping statements (as in while loops , do while loops , and for loops ) allow a sequence of statements to be executed multiple times. Loops can either execute the statements they contain a predefined number of times, or they can execute them repeatedly until some condition is met. Conditional branching statements allow a sequence of statements to be executed only if some condition
2331-564: The call). Early in the development of high-level programming languages , the introduction of the block enabled the construction of programs in which a group of statements and declarations could be treated as if they were one statement. This, alongside the introduction of subroutines , enabled complex structures to be expressed by hierarchical decomposition into simpler procedural structures. Many imperative programming languages (such as Fortran , BASIC , and C ) are abstractions of assembly language . The earliest imperative languages were
2394-595: The code, and so forth. These can be considered flavors of programming paradigm that apply to only parallel languages and programming models. Some programming language researchers criticise the notion of paradigms as a classification of programming languages, e.g. Harper, and Krishnamurthi. They argue that many programming languages cannot be strictly classified into one paradigm, but rather include features from several paradigms. See Comparison of multi-paradigm programming languages . Different approaches to programming have developed over time. Classification of each approach
2457-448: The computer. Higher-level imperative languages use variables and more complex statements, but still follow the same paradigm. Recipes and process checklists , while not computer programs , are also familiar concepts that are similar in style to imperative programming; each step is an instruction, and the physical world holds the state. Since the basic ideas of imperative programming are both conceptually familiar and directly embodied in
2520-410: The data are in the same code unit called an object . This encapsulation ensures that the only way that an object can access data is via methods of the object that contains the data. Thus, an object's inner workings may be changed without affecting code that uses the object. There is controversy raised by Alexander Stepanov , Richard Stallman and other programmers, concerning the efficacy of
2583-433: The dominant language paradigm by the late 1990s. C++ (1985) was originally called "C with Classes." It was designed to expand C's capabilities by adding the object-oriented facilities of the language Simula . An object-oriented module is composed of two files. The definitions file is called the header file . Here is a C++ header file for the GRADE class in a simple school application: A constructor operation
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2646-403: The execution model. For parallel computing , using a programming model instead of a language is common. The reason is that details of the parallel hardware leak into the abstractions used to program the hardware. This causes the programmer to have to map patterns in the algorithm onto patterns in the execution model (which have been inserted due to leakage of hardware into the abstraction). As
2709-534: The expected result, not as a procedure to follow. Given a database or a set of rules, the computer tries to find a solution matching all the desired properties. An archetype of a declarative language is the fourth generation language SQL , and the family of functional languages and logic programming. Functional programming is a subset of declarative programming. Programs written using this paradigm use functions , blocks of code intended to behave like mathematical functions . Functional languages discourage changes in
2772-440: The extent that the developer knows them. Categorizing the resulting code by paradigm is often an academic activity done in retrospect. Languages categorized as imperative paradigm have two main features: they state the order in which operations occur, with constructs that explicitly control that order, and they allow side effects, in which state can be modified at one point in time, within one unit of code, and then later read at
2835-413: The fewest clock cycles to store. The stack is automatically used for the standard variable declarations . Heap memory is returned to a pointer variable from the malloc() function. In the 1970s, software engineers needed language support to break large projects down into modules . One obvious feature was to decompose large projects physically into separate files . A less obvious feature
2898-408: The hardware, most computer languages are in the imperative style. Assignment statements , in imperative paradigm, perform an operation on information located in memory and store the results in memory for later use. High-level imperative languages, in addition, permit the evaluation of complex expressions , which may consist of a combination of arithmetic operations and function evaluations, and
2961-460: The imperative paradigm to a logical extreme, by not having any statements at all, relying purely on commands, even to the extent of making the IF and ELSE commands independent of each other, connected only by an intrinsic variable named $ TEST. COBOL (1960) and BASIC (1964) were both attempts to make programming syntax look more like English. In the 1970s, Pascal was developed by Niklaus Wirth , and C
3024-430: The languages used to code programs. For perspective, other research studies software engineering processes and describes various methodologies to describe and compare them. A programming language can be described in terms of paradigms. Some languages support only one paradigm. For example, Smalltalk supports object-oriented and Haskell supports functional. Most languages support multiple paradigms. For example,
3087-423: The machine languages of the original computers. In these languages, instructions were very simple, which made hardware implementation easier but hindered the creation of complex programs. FORTRAN , developed by John Backus at International Business Machines (IBM) starting in 1954, was the first major programming language to remove the obstacles presented by machine code in the creation of complex programs. FORTRAN
3150-490: The names, arguments, and return types of procedures (and related comments), what a particular procedure is supposed to do, without necessarily looking at the details of how it achieves its result. At the same time, a complete program is still imperative since it fixes the statements to be executed and their order of execution to a large extent. The programming paradigm used to build programs for almost all computers typically follows an imperative model. Digital computer hardware
3213-400: The next. Precise comparisons of competing paradigms' efficacy are frequently made more difficult because of new and differing terminology applied to similar entities and processes together with numerous implementation distinctions across languages. A declarative programming program describes what the problem is, not how to solve it. The program is structured as a set of properties to find in
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#17327804093923276-421: The notion of paradigm as used by Thomas Kuhn in his The Structure of Scientific Revolutions (1962). Early programming languages did not have clearly defined programming paradigms and sometimes programs made extensive use of goto statements. Liberal use of which lead to spaghetti code which is difficult to understand and maintain. This led to the development of structured programming paradigms that disallowed
3339-448: The order independently. More at Comparison of multi-paradigm programming languages . In object-oriented programming, code is organized into objects that contain state that is owned by and (usually) controlled by the code of the object. Most object-oriented languages are also imperative languages. In object-oriented programming, programs are treated as a set of interacting objects. In functional programming , programs are treated as
3402-574: The program should accomplish without specifying all the details of how the program should achieve the result. Procedural programming is a type of imperative programming in which the program is built from one or more procedures (also termed subroutines or functions). The terms are often used as synonyms, but the use of procedures has a dramatic effect on how imperative programs appear and how they are constructed. Heavy procedural programming, in which state changes are localized to procedures or restricted to explicit arguments and returns from procedures,
3465-409: The step by step process that a computer program follows. The efficacy and efficiency of such a program is therefore highly dependent on the programmer's skill. In attempt to improve on procedural languages, object-oriented programming (OOP) languages were created, such as Simula , Smalltalk , C++ , Eiffel , Python , PHP , Java , and C# . In these languages, data and methods to manipulate
3528-510: The use of goto statements; only allowing the use of more structured programming constructs. Machine code is the lowest-level of computer programming as it is machine instructions that define behavior at the lowest level of abstract possible for a computer. As it is the most prescriptive way to code it is classified as imperative. It is sometimes called the first-generation programming language . Assembly language introduced mnemonics for machine instructions and memory addresses . Assembly
3591-489: The use of logical operators such as READ/WRITE/GET/PUT. Assembly was, and still is, used for time-critical systems and often in embedded systems as it gives the most control of what the machine does. Procedural languages , also called the third-generation programming languages are the first described as high-level languages . They support vocabulary related to the problem being solved. For example, These languages are classified as procedural paradigm. They directly control
3654-443: The value of variables through assignment , making a great deal of use of recursion instead. The logic programming paradigm views computation as automated reasoning over a body of knowledge. Facts about the problem domain are expressed as logic formulas, and programs are executed by applying inference rules over them until an answer to the problem is found, or the set of formulas is proved inconsistent. Symbolic programming
3717-479: Was a compiled language that allowed named variables, complex expressions, subprograms, and many other features now common in imperative languages. The next two decades saw the development of many other major high-level imperative programming languages. In the late 1950s and 1960s, ALGOL was developed in order to allow mathematical algorithms to be more easily expressed and even served as the operating system 's target language for some computers. MUMPS (1966) carried
3780-504: Was created by Dennis Ritchie while he was working at Bell Laboratories . Wirth went on to design Modula-2 and Oberon . For the needs of the United States Department of Defense , Jean Ichbiah and a team at Honeywell began designing Ada in 1978, after a 4-year project to define the requirements for the language. The specification was first published in 1983, with revisions in 1995, 2005, and 2012. The 1980s saw
3843-438: Was developed at Dartmouth College for all of their students to learn. If a student did not go on to a more powerful language, the student would still remember Basic. A Basic interpreter was installed in the microcomputers manufactured in the late 1970s. As the microcomputer industry grew, so did the language. Basic pioneered the interactive session . It offered operating system commands within its environment: However,
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#17327804093923906-466: Was either described at the time the approach was first developed, but often not until some time later, retrospectively. An early approach consciously identified as such is structured programming , advocated since the mid 1960s. The concept of a programming paradigm as such dates at least to 1978, in the Turing Award lecture of Robert W. Floyd , entitled The Paradigms of Programming , which cites
3969-519: Was to decompose large projects logically into abstract datatypes . At the time, languages supported concrete ( scalar ) datatypes like integer numbers, floating-point numbers, and strings of characters . Concrete datatypes have their representation as part of their name. Abstract datatypes are structures of concrete datatypes — with a new name assigned. For example, a list of integers could be called integer_list . In object-oriented jargon, abstract datatypes are called classes . However,
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