The primary data structure112 in awk
is the associative array (see Arrays in awk).
Extensions need to be able to manipulate awk arrays.
The API provides a number of data structures for working with arrays,
functions for working with individual elements, and functions for
working with arrays as a whole. This includes the ability to
“flatten” an array so that it is easy for C code to traverse
every element in an array. The array data structures integrate
nicely with the data structures for values to make it easy to
both work with and create true arrays of arrays (see General-Purpose Data Types).