plain-ltx – Make plain TeX files LaTeXable

The pack­age plain.sty de­fines a LaTeX en­vi­ron­ment which can pro­cess a doc­u­ment writ­ten to use Knuth's ba­sic Plain TeX macros.
In­side the en­vi­ron­ment, not ev­ery­thing is as Knuth in­tended (some Plain com­mands are sup­pressed, some are faked, and some ba­sic mech­a­nisms—such as font se­lec­tion and the out­put rou­tine—re­main as in LaTeX). Thus “sim­ple” doc­u­ments will run, but elab­o­rate macros de­fined in the doc­u­ment have a chance of fail­ing.