Why is it necessary to compile 4 times when using bibliography?

Question

I am writing a paper with TexMaker and I and handling the bibliography apart in a bibliography.bib as I think it is more efficient and clean.

To include it I need to set the command

\bibliography{bibliography}

and every time I want a citation I write

\cite{label}

Allright. It took me a while to be able to see the citations and references, until I discovered that I had to write next compilation sequence:

1- PDFLatex

2- BibTex

3- PDFLatex

4- PDFLatex

Why is it necessary to compile 4 times to be able to see changes in bibliography?

Answer 1

Well lets assume that you have a number style, so \cite{knuth} should at the end give "see [3]" in the text and "[3] Knuth, The TeXbook" in the bibliography.

The information is gathered in this way:

1. In the first pdflatex run, latex writes \citation{knuth} to the aux-file, and an information about the bib-files and the style you want to use.
2. The bibtex run uses the informations of the aux file to generate from the bib-files a bbl-file which contains the bibliography with all the sources you want to cite (sorted and formated).
3. In the second pdflatex run, latex prints the bibliography from the bbl file and while doing this extract the numbers associated to a key and stores it again in the aux-file: \bibcite{knuth}{3}.
4. In the next run pdflatex uses this informations to update the number in you text "see [3]".
5. As this can change the formatting of your text you perhaps need more runs to update page references.

If you use biblatex with biber things are bit different, as biber doesn't use the aux-file but needs its informations in a bcf-file but the principe is similar