For this reason, most programming languages support the use of variables . This is a computer-oriented variant of scientific notation , using binary fractions and exponents. Rather, it is used for a command. In our example above, cartons and sauce pans are both used to contain eggs. We could model either of these containers as an ordered set of values, or list .
Lists contain items and have ways to insert and remove items.
The exact order of items in a list may not be critical in a given application. For instance, eggs have no particular ordering in a carton or pan. If, on the other hand, we were modelling a package-handling system, the ordering of items in our lists might be very important, indeed. Finally, by combining basic forms, it is possible to create structures that are even more complex. For instance, it is quite possible to consider using trees of arrays, stacks of queues, hashes of arrays, and more.