# Is TeX necessary if using LaTeX?

I have been using LaTeX for a little over two years now. I mostly use it to prepare homework solutions in mathematics and engineering coursework. I also use it to document my research and writing some reports.

Recently I have started to use it for my resume, because I find the formatting to be significantly more stable than anything I can get using Microsoft Word. However, I have not been able to find a satisfactory resume class, so I am now modifying a resume class to suit my needs.

To improve the resume class, I am now trying to make some new environments and commands to make the construction more intuitive. The class file that I am modifying appears to be in Plain TeX, which inspires my question.

Are there certain layout and design problems that can only be solved using Plain TeX, or can everything be done using LaTeX?

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I think that Leslie Lamport answered part of this question in the first chapter of his book LaTeX: A Document Preparation System: "Think of LaTeX as a house built with the lumber and nails provided by TeX. You don't need lumber and nails to live in a house, but they are handy for adding an extra room. Most LaTeX users never need to know any more about TeX commands than they can learn from this book. However, the lower-level TeX commands described in the TeXbook can be very useful when creating a new package for LaTeX." –  Gonzalo Medina Sep 15 '12 at 19:16

Apart from the output routine code, almost all the macros defined in Plain TeX are also in LaTeX, so when you look into a class file you may well see code that uses those commands, and in particular includes TeX primitive commands (such as \hbox or \vskip).