FOCAL (programming language)
level programming language for the Lego Mindstorms NXT
FOCAL (acronym for Formulating On-line Calculations in Algebraic Language, or FOrmula CALculator) is an interactive interpreted programming language based on JOSS and mostly used on Digital Equipment Corporation (DEC) PDP series machines.
JOSS was designed to be an interactive language to allow programs to be easily written by non-programmers. FOCAL is very similar to JOSS in the commands it supports and the general syntax of the language. It differs in that many of JOSS' advanced features like ranges and user-defined functions were removed to simplify the parser and allow the system to run in less memory. Some of the reserved words (keywords) were renamed so that they all start with a unique first letter. This allows users to type in programs using one-character statements, further reducing memory needs. This was an important consideration on the PDP-8, which was often limited to a few kilobytes (KB).
Like JOSS, and later BASICs, FOCAL on the PDP-8 was a complete environment that included a line editor, an interpreter, and input/output routines. The package as a whole was named FOCAL-8, which also ran on the PDP-5 and PDP-12. When ported to the PDP-11, the resulting FOCAL-11 relied on the underlying operating system, RT-11, to provide file support and editing.
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Vocabulary and entity names are the principal evidence signals here, because they determine the precision of every later search. The source revision retrieved here is dated Jun 10, 2026. The linked authority identifier is Q1966202. 1 of 1 selected statements include explicit references; 0 carry qualifiers and 0 use preferred rank.
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This entry incorporates text from “FOCAL (programming language)” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.