Editing FOCAL (programming language) (section)

{{Short description|Programming language used on DEC PDP-series machines}}
{{For|the unrelated set of programming-related features on HP41 calculators|FOCAL (Hewlett-Packard)}}
{{Infobox programming language
| name = FOCAL
| paradigm = [[Imperative programming|imperative]]
| family = [[JOSS]]
| designer = Richard Merrill
| developer = [[Digital Equipment Corporation|DEC]]
| released = {{Start date and age|1968}}
| discontinued = Yes
| influenced by = [[JOSS]]
| influenced = [[BASIC-PLUS]]
| website = 
}}
'''FOCAL''' (acronym for '''Formulating On-line Calculations in Algebraic Language''',{{sfn|Manual|1968|p=1.1}} or '''FOrmula CALculator'''<ref>{{cite book |url=http://bitsavers.org/pdf/dec/_Books/DEC_1957_To_The_Present_1978.pdf |title=DEC, 1957 to the Present |publisher=DEC |date=1978 |page=38}}</ref>) is an interactive [[Interpreter (computing)|interpreted]] [[programming language]] based on [[JOSS]] and mostly used on [[Digital Equipment Corporation]] (DEC) [[Programmed Data Processor|PDP]] series machines.

JOSS was designed to be a simple 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 (programming languages)|syntax]] of the language. It differs in that many of JOSS' advanced features like [[Range (computer programming)|ranges]] and [[user-defined function]]s were removed to simplify the [[parser]] and allow the system to run in less memory. Some of the [[reserved word]]s (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 [[kilobyte]]s (KB).

Like JOSS, and later [[BASIC]]s, FOCAL on the PDP-8 was a complete environment that included a [[line editor]], an [[Interpreter (computing)|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. The language definition was updated twice, to ''FOCAL-69'' and a very slightly modified ''FOCAL-71''. A port to the [[Intel 8080]] was also available.

FOCAL is notable as the language in which the original versions of the early [[video game]]s [[Hamurabi (video game)|''Hamurabi'']] and [[Lunar Lander (video game genre)|''Lunar Lander'']] were written. Both were later ported to BASIC, where they became much better known.<ref name="TIME">{{cite magazine |url=https://time.com/69316/basic/ |title=Fifty Years of BASIC, the Programming Language That Made Computers Personal |magazine=[[Time (magazine)|Time]] |last=McCracken |first=Harry |date=2014-04-29 |access-date=2016-02-12 |archive-url=https://web.archive.org/web/20160205214236/http://time.com/69316/basic/ |archive-date=2016-02-05 |url-status=live}}</ref> FOCAL was not popular outside the PDP platform and largely disappeared during the move to the [[VAX-11]]. It had a strong revival in the [[Soviet Union]] where PDP-11 clones were used as educational and [[home computer]]s ([[Electronika BK|BK series]]).