It is Pascal, which is then used to compile the original TeX code. See example of running TeX/LaTeX at [1].
PGF/TikZ is a very well written program. What impresses me is that it does have the right amount of abstraction. It comes in different layers, starting from the Front End (TikZ), Basic Layer (which TikZ) uses This layer is built on top of the system layer. Whereas the
system layer just provides the absolute minimum for drawing graphics, the basic layer provides numerous
commands that make it possible to create sophisticated graphics easily and also quickly.
The basic layer does not provide a convenient syntax for describing graphics, which is left to frontends
like TikZ. For this reason, the basic layer is typically used only by “other programs”. For example, the
beamer package (can be used for presentations) uses the basic layer extensively, but does not need a convenient input syntax. Rather,speed and flexibility are needed when beamer creates graphics
The system layer, and drivers then create the the graphics in various formats, such as postscript, pdf etc.
PGF/TikZ is a very well written program. What impresses me is that it does have the right amount of abstraction. It comes in different layers, starting from the Front End (TikZ), Basic Layer (which TikZ) uses This layer is built on top of the system layer. Whereas the system layer just provides the absolute minimum for drawing graphics, the basic layer provides numerous commands that make it possible to create sophisticated graphics easily and also quickly.
The basic layer does not provide a convenient syntax for describing graphics, which is left to frontends like TikZ. For this reason, the basic layer is typically used only by “other programs”. For example, the beamer package (can be used for presentations) uses the basic layer extensively, but does not need a convenient input syntax. Rather,speed and flexibility are needed when beamer creates graphics
The system layer, and drivers then create the the graphics in various formats, such as postscript, pdf etc.
[1] https://tex.rossprogram.org/