How models run - a very simple overview

How the models run (execute). Some models are compiled, which makes them fast = computationally efficient. Others are interpreted line-by-line each time they are run, such as program written (at least originally) in Matlab or java. They're much slower, but they can often be modified quickly. Some models are inherently interactive, prompting one for inputs sequentially. Others run in batch mode, asking for all inputs from a data file. Of course, one can take an interactive model (e.g., running as a standalone application on a PC or a UNIX station) and redirect its input to be from a file; it becomes a batch-mode program.