In computer programming, a free-form language is a programming language in which the positioning of characters on the page in program text is insignificant. Program text does not need to be placed in specific columns as on old punched card systems, and frequently ends of lines are insignificant. Whitespace characters are used only to delimit tokens, and have no other significance.
Most free-form languages descend from ALGOL, including C, Pascal, and Perl. Lisp languages are free-form, although they do not descend from ALGOL. Rexx is mostly free-form, though in some cases whitespace characters are concatenation operators. SQL, though not a full programming language, is also free-form.
Most free-form languages are also structured programming languages, which is sometimes thought to go along with the free-form syntax: Earlier imperative programming languages such as Fortran 77 used particular columns for line numbers, which many structured languages do not use or need.
Structured languages exist which are not free-form, such as ABC, Curry, Haskell, Python and others. Many of these use some variant of the off-side rule, in which indentation, rather than keywords or braces, is used to group blocks of code.
ALGOL is a family of imperative computer programming languages originally developed in 1958. ALGOL heavily influenced many other languages and was the standard method for algorithm description used by the Association for Computing Machinery (ACM) in textbooks and academic sources until object-oriented languages came around, for more than thirty years.
C is a general-purpose, procedural computer programming language supporting structured programming, lexical variable scope, and recursion, with a static type system. By design, C provides constructs that map efficiently to typical machine instructions. It has found lasting use in applications previously coded in assembly language. Such applications include operating systems and various application software for computers architectures that range from supercomputers to PLCs and embedded systems.
Rebol is a cross-platform data exchange language and a multi-paradigm dynamic programming language designed by Carl Sassenrath for network communications and distributed computing. It introduces the concept of dialecting: small, optimized, domain-specific languages for code and data, which is also the most notable property of the language according to its designer Carl Sassenrath:
Although it can be used for programming, writing functions, and performing processes, its greatest strength is the ability to easily create domain-specific languages or dialects
A text editor is a type of computer program that edits plain text. Such programs are sometimes known as "notepad" software, following the naming of Microsoft Notepad. Text editors are provided with operating systems and software development packages, and can be used to change files such as configuration files, documentation files and programming language source code.
In computer science, Backus–Naur form or Backus normal form (BNF) is a notation technique for context-free grammars, often used to describe the syntax of languages used in computing, such as computer programming languages, document formats, instruction sets and communication protocols. They are applied wherever exact descriptions of languages are needed: for instance, in official language specifications, in manuals, and in textbooks on programming language theory.
In computer science, lexical analysis, lexing or tokenization is the process of converting a sequence of characters into a sequence of tokens. A program that performs lexical analysis may be termed a lexer, tokenizer, or scanner, although scanner is also a term for the first stage of a lexer. A lexer is generally combined with a parser, which together analyze the syntax of programming languages, web pages, and so forth.
In computer programming, an indentation style is a convention governing the indentation of blocks of code to convey program structure. This article largely addresses the free-form languages, such as C and its descendants, but can be applied to most other programming languages, where whitespace is otherwise insignificant. Indentation style is only one aspect of programming style.
YAML is a human-readable data-serialization language. It is commonly used for configuration files and in applications where data is being stored or transmitted. YAML targets many of the same communications applications as Extensible Markup Language (XML) but has a minimal syntax which intentionally differs from SGML. It uses both Python-style indentation to indicate nesting, and a more compact format that uses [...] for lists and {...} for maps making YAML 1.2 a superset of JSON.
Prettyprint is the application of any of various stylistic formatting conventions to text files, such as source code, markup, and similar kinds of content. These formatting conventions can adjust positioning and spacing, add color and contrast, adjust size, and make similar modifications intended to make the content easier for people to view, read, and understand. Prettyprinters for programming language source code are sometimes called code beautifiers.
The tab keyTab ↹ on a keyboard is used to advance the cursor to the next tab stop.
Non-English-based programming languages are programming languages that do not use keywords taken from or inspired by English vocabulary.
A computer programming language is said to adhere to the off-side rule if blocks in that language are expressed by their indentation. The term was coined by Peter J. Landin, possibly as a pun on the offside rule in football. This is contrasted with free-form languages, notably curly-bracket programming languages, where indentation is not meaningful and indent style is only a matter of convention and code formatting.
ALGOL 60 is a member of the ALGOL family of computer programming languages. It followed on from ALGOL 58 which had introduced code blocks and the begin and end pairs for delimiting them, representing a key advance in the rise of structured programming. ALGOL 60 was the first language implementing nested function definitions with lexical scope. It gave rise to many other programming languages, including CPL, Simula, BCPL, B, Pascal, and C. Practically every computer of the era had a systems programming language based on ALGOL 60 concepts.
ALGOL 68 is an imperative programming language that was conceived as a successor to the ALGOL 60 programming language, designed with the goal of a much wider scope of application and more rigorously defined syntax and semantics.
In computer science, a relational operator is a programming language construct or operator that tests or defines some kind of relation between two entities. These include numerical equality and inequalities.
In computer programming, a one-pass compiler is a compiler that passes through the parts of each compilation unit only once, immediately translating each part into its final machine code. This is in contrast to a multi-pass compiler which converts the program into one or more intermediate representations in steps between source code and machine code, and which reprocesses the entire compilation unit in each sequential pass.
In computer programming, whitespace is any character or series of characters that represent horizontal or vertical space in typography. When rendered, a whitespace character does not correspond to a visible mark, but typically does occupy an area on a page. For example, the common whitespace symbol U+0020SPACE represents a blank space punctuation character in text, used as a word divider in Western scripts.
In computer language design, stropping is a method of explicitly marking letter sequences as having a special property, such as being a keyword, or a certain type of variable or storage location, and thus inhabiting a different namespace from ordinary names ("identifiers"), in order to avoid clashes. Stropping is not used in most modern languages – instead, keywords are reserved words and cannot be used as identifiers. Stropping allows the same letter sequence to be used both as a keyword and as an identifier, and simplifies parsing in that case – for example allowing a variable named if without clashing with the keyword if.
This comparison of programming languages compares the features of language syntax (format) for over 50 computer programming languages.
In computer languages, identifiers are tokens which name language entities. Some of the kinds of entities an identifier might denote include variables, types, labels, subroutines, and packages.
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