Logo (programming language)

Logo (programming language)
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Name	Logo
Paradigm	Multi-paradigm (functional, educational, procedural, reflective)
Designer	Wally Feurzeig, Seymour Papert, Cynthia Solomon
Developer	Bolt, Beranek and Newman
Released	0 1967
Influenced	Smalltalk, Scheme, NetLogo, Scratch

Logo (programming language). Logo is an educational programming language created in the late 1960s. It is renowned for its use of turtle graphics, where commands control an on-screen or robotic cursor. The language was designed to teach concepts of programming and mathematical thinking to children and beginners.

History and development

Logo was conceived in 1966 at Bolt, Beranek and Newman, a firm with deep ties to the early ARPANET and AI research. The principal designers were Wally Feurzeig and Seymour Papert, with significant contributions from Cynthia Solomon. Papert, a mathematician who worked with Jean Piaget in Geneva, was heavily influenced by constructivist learning theories. The language drew direct inspiration from Lisp, particularly its use of symbols and recursion, but was simplified for accessibility. Early development was supported by the National Science Foundation and the Massachusetts Institute of Technology, where Papert co-founded the MIT Media Lab. The first implementation ran on a DEC PDP-1 computer, and the language gained wider prominence through projects like the MIT Logo Group and the Apple II computer.

Core concepts and the turtle

The central innovation of Logo is the turtle, an on-screen or physical robotic object whose movement generates graphics. The turtle exists in a state defined by its position and heading on a Cartesian plane. Fundamental commands like `FORWARD`, `BACK`, `RIGHT`, and `LEFT` manipulate this state, allowing users to draw geometric shapes. This concrete, spatial metaphor makes abstract concepts like procedures, loops, and variables tangible. The turtle's environment encourages exploration of ideas from geometry, trigonometry, and even differential geometry. This approach, termed "body-syntonic" learning by Papert, allowed students to project their own sense of movement and space onto the programming object.

Syntax and language features

Logo's syntax is notable for its use of "word and list processing", inherited from its Lisp roots. Data types primarily include words and lists, which can be easily manipulated. The language supports modularity through user-defined procedures, which can call themselves, enabling powerful recursive algorithms. Control structures include `REPEAT`, iterative `FOR`, and conditional `IF` statements. A key feature is its extensible nature; new commands are defined simply, encouraging learners to build their own vocabulary. Logo also supports multiple turtles and object-oriented extensions in later dialects. Its interpreter typically operates in a REPL environment, providing immediate feedback.

Educational use and impact

Logo became a cornerstone of the computers in education movement during the 1980s. Its philosophy, detailed in Papert's influential book *Mindstorms*, argued that children could use computers as "Objects to think with" to construct knowledge. Major projects like the one at the Lamplighter School in Texas demonstrated its potential. While its adoption in standard curricula was uneven, its principles directly influenced later constructionist tools and environments. The language's legacy is evident in modern educational platforms like the MIT Media Lab's Scratch and the LEGO Mindstorms robotics kits, which bear Papert's advisory influence. Research on Logo's effectiveness sparked ongoing debates within the ACM and ISTE about the role of programming in learning.

Implementations and dialects

Hundreds of Logo implementations have been created for nearly every computing platform since the 1970s. Early significant versions included Apple Logo for the Apple II and Terrapin Logo for the 6502-based machines. UCBLogo (later known as Berkeley Logo) became a widely used standard. The language fragmented into many dialects, such as StarLogo (and its successor NetLogo) for agent-based modeling, and MSWLogo for Windows environments. Commercial versions were marketed by companies like LCSI (Logo Computer Systems Inc.). Specialized variants also controlled physical robots from manufacturers like LEGO and Texas Instruments. The open-source GNU project produced GNU Logo, ensuring the language's continued availability and adaptation to new systems like Linux and macOS.

Category:Educational programming languages Category:Lisp programming language family Category:Procedural programming languages Category:Programming languages created in 1967