With a C-like array or a vector, each item is associated with its numeric index. Earlier this was exploited in one of the examples in the section on vector in which the index provided the decile of the distribution and, conveniently, the distribution was split in a way that the ten deciles of data are numbered.
An associative container allows you to provide indexes that are not numeric; these are the keys, and you can associate values with them. As you insert key-value pairs into the container, they will be ordered so that the container can subsequently efficiently access the value by its key. Typically, this order should not matter to you since you will not use the container to access items sequentially, and instead ...
