ABC is an imperative general-purpose

programming language A programming language is a system of notation for writing computer programs. Programming languages are described in terms of their Syntax (programming languages), syntax (form) and semantics (computer science), semantics (meaning), usually def ...

and

integrated development environment An integrated development environment (IDE) is a Application software, software application that provides comprehensive facilities for software development. An IDE normally consists of at least a source-code editor, build automation tools, an ...

(IDE) developed at Centrum Wiskunde & Informatica (CWI), in

Amsterdam Amsterdam ( , ; ; ) is the capital of the Netherlands, capital and Municipalities of the Netherlands, largest city of the Kingdom of the Netherlands. It has a population of 933,680 in June 2024 within the city proper, 1,457,018 in the City Re ...

Netherlands , Terminology of the Low Countries, informally Holland, is a country in Northwestern Europe, with Caribbean Netherlands, overseas territories in the Caribbean. It is the largest of the four constituent countries of the Kingdom of the Nether ...

by Leo Geurts, Lambert Meertens, and Steven Pemberton. It is interactive, structured, high-level, and intended to be used instead of

BASIC Basic or BASIC may refer to: Science and technology * BASIC, a computer programming language * Basic (chemistry), having the properties of a base * Basic access authentication, in HTTP Entertainment * Basic (film), ''Basic'' (film), a 2003 film ...

, Pascal, or AWK. It is intended for teaching or prototyping, but not as a systems-programming language. ABC had a major influence on the design of the language Python, developed by

Guido van Rossum Guido van Rossum (; born 31 January 1956) is a Dutch programmer. He is the creator of the Python programming language, for which he was the " benevolent dictator for life" (BDFL) until he stepped down from the position on 12 July 2018. He ...

, who formerly worked for several years on the ABC system in the mid-1980s.

Features

Its designers claim that ABC programs are typically around a quarter the size of the equivalent Pascal or C programs, and more readable. Key features include: *Only five basic

data type In computer science and computer programming, a data type (or simply type) is a collection or grouping of data values, usually specified by a set of possible values, a set of allowed operations on these values, and/or a representation of these ...

s *No required variable declarations *Explicit support for

top-down programming Bottom-up and top-down are strategies of composition and decomposition in fields as diverse as information processing and ordering knowledge, software, humanistic and scientific theories (see systemics), and management and organization. In p ...

*Statement nesting is indicated by

indentation __FORCETOC__ In the written form of many languages, indentation describes empty space ( white space) used before or around text to signify an important aspect of the text such as: * Beginning of a paragraph * Hierarchy subordinate concept * Qu ...

, via the

off-side rule The off-side rule describes syntax of a computer programming language that defines the bounds of a code block via indentation. The term was coined by Peter Landin, possibly as a pun on the offside law in association football. An off-side ...

* Infinite precision arithmetic, unlimited-sized lists and strings, and other features supporting orthogonality and ease of use by novices * Polymorphic commands and functions * Interactive environment with command completion, persistent workspaces, and no separate file handling ABC was originally a monolithic implementation, leading to an inability to adapt to new requirements, such as creating a

graphical user interface A graphical user interface, or GUI, is a form of user interface that allows user (computing), users to human–computer interaction, interact with electronic devices through Graphics, graphical icon (computing), icons and visual indicators such ...

(GUI). ABC could not directly access the underlying file system and

operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...

. The full ABC system includes a programming environment with a structure editor (syntax-directed editor), suggestions,

static variable In computer programming, a static variable is a variable that has been allocated "statically", meaning that its lifetime (or "extent") is the entire run of the program. This is in contrast to shorter-lived automatic variables, whose storage is ...

s (persistent), and multiple workspaces, and is available as an

interpreter Interpreting is translation from a spoken or signed language into another language, usually in real time to facilitate live communication. It is distinguished from the translation of a written text, which can be more deliberative and make use o ...

–

compiler In computing, a compiler is a computer program that Translator (computing), translates computer code written in one programming language (the ''source'' language) into another language (the ''target'' language). The name "compiler" is primaril ...

. , the latest version is 1.05.02, and it is ported to

Unix Unix (, ; trademarked as UNIX) is a family of multitasking, multi-user computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, a ...

DOS DOS (, ) is a family of disk-based operating systems for IBM PC compatible computers. The DOS family primarily consists of IBM PC DOS and a rebranded version, Microsoft's MS-DOS, both of which were introduced in 1981. Later compatible syste ...

Atari Atari () is a brand name that has been owned by several entities since its inception in 1972. It is currently owned by French holding company Atari SA (formerly Infogrames) and its focus is on "video games, consumer hardware, licensing and bl ...

, and Apple

MacOS macOS, previously OS X and originally Mac OS X, is a Unix, Unix-based operating system developed and marketed by Apple Inc., Apple since 2001. It is the current operating system for Apple's Mac (computer), Mac computers. With ...

Example

An example function to collect the set of all words in a document: HOW TO RETURN words document: PUT IN collection FOR line IN document: FOR word IN split line: IF word not.in collection: INSERT word IN collection RETURN collection

Implementations

ABC has been through multiple iterations, with the current version being the 4th major release. Implementations exist for Unix-like systems, MS-DOS/Windows, Macintosh, and other platforms. The source code was made available via Usenet in the late 1980s/early 1990s.

Features

Example

Implementations

References

Further reading