# Where I can find the source code of pdflatex.exe?

Where I can find the source code of pdflatex.exe?

## Edit 1

This is quoted from the link given by @TH.

pdfTeX is built on top of TeX, written by Donald Knuth cum suis (Liang and so), and eTeX, written by Peter Breitenlohner cum suis; part of the paragraph optimization is inspired by the work of Hermann Zapf.

Does it imply that the source code of pdflatex.exe will invoke TeX and eTeX ?

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Good question: does pdf(la)tex always imply eTeX? –  Martin Scharrer Mar 9 '11 at 9:15
@Martin: pdfTeX contains the e-TeX extensions. See the introduction to the pdfTeX manual. –  TH. Mar 9 '11 at 9:19

Edit:
To answer your follow up question, pdflatex does not invoke tex or etex. Rather, pdfTeX implements the ε-TeX extensions.

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@TH. : thanks. By the way what is the difference between pdftex.exe and pdflatex.exe ? Please see my update also. –  xport Mar 9 '11 at 9:02
@xport pdflatex is a shortcut for pdftex -fmt=pdflatex. See pdftex -help. –  Andrey Vihrov Mar 9 '11 at 9:13
@Andrey: Oh, pdflatex.exe = pdftex.exe -fmt=pdflatex. Unbelievable. –  xport Mar 9 '11 at 9:27
@xport: There are four ways to choose a format: the (base) name of the binary (e.g., pdflatex), via &format (e.g., pdftex &pdflatex, via -fmt (e.g., pdftex -fmt pdflatex), and via the first line of the input file (e.g., %&pdflatex). –  TH. Mar 9 '11 at 9:32
@TH. : So the definition of pdflatex must exist first because it will be used by pdftex. It does not make sense actually. In my mental model, pdftex is more mature than pdflatex. –  xport Mar 9 '11 at 9:39