\usepackage{iftex} \ifPDFTeX \ifXeTeX \ifLuaTeX
\usepackage{iftex,ifpdf} \ifPDFTeX %%% pdftex ¿£Áø \ifpdf %%% pdf output mode ..... \else %%% dvi output mode, dvips or dvipdfmx .... \fi \else\ifXeTeX %%% xetex ¿£Áø ... \else\ifLuaTeX %%% luatex ¿£Áø ... \fi\fi\fi