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What's in a Name: A Guide to the Many Flavours of TeX

Contents

1 Introduction

1.1 The context: 40 years of development

1.2 TeX is not just for mathematics

2 The genesis of TeX: A brief history

2.1 TeX was a huge success

3 Knuth still maintains TeX, but new “versions” have evolved

3.1 What’s in a name?

3.2 LaTeX: a set of macros, not a TeX engine

4 So, what does TeX actually do?

4.1 Understanding TeX’s programmability

4.2 TeX the program and TeX the programming language

5 And finally: from TeX to pdfTeX, XeTeX and LuaTeX

5.1 Primitives are not the whole story: TeX macros

5.2 So, finally, what is LaTeX?

6 From TeX engines to TeX installations

6.1 Key features of pdfTeX, XeTeX and LuaTeX

6.2 TeX installations: TeX Live

7 Overleaf: Supporting the LaTeX ecosystem

7.1 Overleaf: LaTeX solutions for authors and institutions

7.1.1 Overleaf for authors

7.1.2 Overleaf for institutions and enterprises

Introduction

Perhaps you’ve heard of, or read about, something called “TeX”, “LaTeX” or “pdfLaTeX”—or any one of the multitude of similar-sounding terms—but you aren’t quite sure what they actually mean? If so, then this article is for you: a non-technical background to explain the many variations of TeX-based software—what they mean and why they exist. For the moment we’ll simplify the discussion by using the generic term “TeX” but later we’ll give the context and meaning of its many derivatives and variations: LaTeX, pdfTeX, pdfLaTeX, XeTeX, XeLaTeX, LuaTeX, and LuaLaTeX. You might have seen some of those terms within Overleaf’s menu where it allows you to select your preferred “Compiler”:

Unless you are a seasoned TeX user, or familiar with its ecosystem, the many “varieties of TeX” can be confusing; however, by the end of this article you should feel much more informed and at ease when engaging with any colleagues, authors or journal editors who are conversant with TeX-based terminology.

The context: 40 years of development

TeX’s roots date back to the late 1970s and the decades following its creation have seen the development of numerous TeX-based typesetting programs which provide considerable enhancements and additional functionality compared to the original TeX program. Those new to STM publishing, or considering it as a career, may be surprised to learn that typesetting software whose origins date back some 40 years is still in widespread use by technical authors—and forms a critical component of many modern publishing workflows through services such as Overleaf.

TeX is not just for mathematics

It is a common, though understandable, misconception that the use of TeX is restricted to scientific and technical disciplines; specifically, the typesetting of complex mathematics. Whilst it finds most users in those domains, TeX-based software is widely used for the production of non-mathematical content—because of its high quality of output and incredible versatility. In addition to typesetting mathematics, the latest versions of TeX (called XeTeX and LuaTeX) support modern font technologies (OpenType), Unicode-based text input, OpenType-based math fonts (as pioneered by Microsoft Word), multilingual typesetting (including Arabic and other complex scripts), direct output to PDF and much more besides. For example, here is a demonstration of XeTeX’s multilingual typesetting with complex-script languages, including Arabic, Sanskrit, Hindi, Chinese, Japanese, Korean, Greek and Thai. Or, if you are interested in cooking, how about producing a recipe booklet?

The genesis of TeX: A brief history

The American historian Daniel J. Boorstin once noted that:

“Trying to plan for the future without a sense of history is like trying to plant cut flowers.”

In keeping with the ethos of that quote we’ll start with a brief history of TeX: where did it come from, who created it—and why?

On 30 March 1977 the diary of Professor Donald Knuth, a computer scientist at Stanford University, recorded the following note to express his dissatisfaction with the quality of typeset proofs he’d just received for volume 2 of his book series The Art of Computer Programming:

“Galley proofs for vol. 2 finally arrive, they look awful... (typographically). I decide I have to solve the problem myself.”

The quote above is from page 482 of Digital Typography by Donald E. Knuth.<br>That small entry in Professor Knuth’s diary marked the catalyst for a programming journey which lasted many years and resulted in the creation of typesetting software capable of producing exquisitely typeset mathematics and, of course, beautifully typeset text: a program that Knuth named TeX.

Knuth is a brilliant computer scientist and whilst developing TeX he, and his colleagues, designed new and sophisticated algorithms to solve some very complex typesetting problems: including automatic line...