Editing Transclusion (section)

==Origins==
The concept of reusing file content began with computer programming languages: [[COBOL]] in 1960,<ref>{{Cite book|url=http://bitsavers.trailing-edge.com/pdf/codasyl/COBOL_Report_Apr60.pdf#page=56|title=Initial Specifications for a COMMON BUSINESS ORIENTED LANGUAGE (COBOL) for Programming Electronic Digital Computers|date=April 1960|publisher=Department of Defense|location=Washington|pages=V-27|quote=INCLUDE: Function: To save the programmer effort by automatically incorporating library subroutines into the source program.}}</ref> followed by [[BCPL]], [[PL/I]], [[C (programming language)|C]],<ref>{{Cite journal <!-- Citation bot bypass-->|last=Ritchie|first=Dennis M.|author-link=Dennis Ritchie|date=1993-03-01|title=The development of the C language|journal=ACM SIGPLAN Notices|language=EN|volume=28|issue=3|pages=201–208|doi=10.1145/155360.155580|url=https://dl.acm.org/doi/abs/10.1145/155360.155580|archive-url=https://web.archive.org/web/20200227090139/https://dl.acm.org/doi/abs/10.1145/155360.155580|archive-date=27 February 2020|quote=Many other changes occurred around 1972-3, but the most important was the introduction of the [[C preprocessor|preprocessor]], partly at the urging of Alan Snyder [Snyder 74], but also in recognition of the utility of the the[sic]<!--Original source has the duplicate word! --> file-inclusion mechanisms available in [[BCPL]] and [[PL/I]]. Its original version was exceedingly simple, and provided only included files and simple [[Sed#Substitution command|string replacements]]: [[Include directive|#include]] and #define of parameterless macros. Soon thereafter, it was extended, mostly by [[Mike Lesk]] and then by John Reiser, to incorporate [[Macro (computer science)#Parameterized macro|macros with arguments]] and [[conditional compilation]]. The preprocessor was originally considered an optional adjunct to the language itself.}} [http://www.jslint.com/chistory.html Alt URL] {{Webarchive|url=https://web.archive.org/web/20200204075428/http://jslint.com/chistory.html |date=2020-02-04 }}</ref> and by 1978, even [[Fortran#Transition to ANSI Standard Fortran|FORTRAN]]. An [[include directive]] allows common [[source code]] to be reused while avoiding the pitfalls of [[Copy-and-paste programming|copy-and-paste-programming]] and [[hard coding]] of constants. As with many innovations, a problem developed. Multiple include directives may provide the same content as another include directive, inadvertently causing repetitions of the same source code into the final result, resulting in an [[Syntax error|error]]. [[Include guard]]s help solve this by, after a single inclusion of content, thereafter omitting the duplicate content.<ref>{{Cite book|last1=Stallman|first1=Richard M.|chapter-url=https://scicomp.ethz.ch/public/manual/gcc/6.3.0/cpp.pdf#page=14|title=The C Preprocessor: For gcc version 6.3.0 (GCC)|last2=Weinberg|first2=Zachary|pages=10–11|chapter=Header Files|quote=Alternatives to Wrapper #ifndef : [[C preprocessor|CPP]] supports two more ways of indicating that a header file should be read only once. Neither one is as portable as a wrapper ‘#ifndef’ and we recommend you do not use them in new programs, with the caveat that ‘#import’ is standard practice in [[Objective-C]]. [...] Another way to prevent a header file from being included more than once is with the ‘[[pragma once|#pragma once]]’ directive. If ‘#pragma once’ is seen when scanning a header file, that file will never be read again, no matter what.|author-link=Richard Stallman}}</ref>

The idea of a single, reusable, source for information lead to concepts like: [[Don't repeat yourself]] and the [[Abstraction principle (computer programming)|abstraction principle]]. A further use was found to make programs more [[Software portability|portable]]. Portable source code uses an include directive to specify a [[C file input/output|standard library]], which contains system specific source code that varies with each computer environment.<ref>{{Cite journal|last1=Johnson|first1=S. C.|author-link=Stephen C. Johnson|last2=Ritchie|first2=D. M.|author-link2=Dennis Ritchie|date=July–August 1978|title=UNIX time-sharing system: Portability of C programs and the UNIX system|journal=The Bell System Technical Journal|volume=57|issue=6|pages=2021–2048|doi=10.1002/j.1538-7305.1978.tb02141.x|s2cid=17510065|issn=0005-8580|access-date=27 February 2020|url=https://ieeexplore.ieee.org/document/6770409|quote=Even before the advent of the [[Interdata 7/32 and 8/32|Interdata]] machine, it as realized, as mentioned above, that many programs depended to an undesirable degree not only on [[Unix|UNIX]] I/O conventions but on details of particularly favorable buffering strategies for the [[PDP-11]]. A package of routines, called the "[[C file input/output|portable I/O library]]," was written by [[Mike Lesk|M. E. Lesk]] and implemented on the [[Honeywell 6000 series|Honeywell]] and IBM machines as well as the PDP-11 in a generally successful effort to overcome the deficiencies of earlier packages}}</ref>