{Data structures in \eTeX} {Karel Skoup\'y} {For the construction of macro packages, \TeX\ is used as a programming language. Unlike general programming languages it lacks complex data structures. We present the experience of providing record and array data structures and the supporting operations using \eTeX\ features. They were successfully applied in real projects for parametrization and as a base for special table module involving complex dimension calculations. We will show how the abstraction level provided by more powerful data-structures can simplify and unify \TeX\ low-level code. }