The
Simulink^{®} MDL model file contains information about block placements
and parameters, connection lines between blocks, model parameters. Block
parameters can consist of simple numbers and vectors, as well as more complex
MATLAB® expressions, such as variables, vectors of expressions [1 1/x], and
expressions like eye (3, 3). These variables are initialized by scripts.

For simple models, you may have only a single MDL file to describe to the model. However, more complex models usually have additional files associated with them. These files include:

•**Scripts (also called M files):** These files contain such things as
initial data values and block open functions.

•**DLLs or MATLAB executables:** Some blocks (such as S-function based
blocks) are implemented as DLLs or MATLAB executables (M or MEX files).

•**Binary data files (MAT):** These files contain variables and their
values in binary format.

•**Block libraries (MDL):** The original model contains reference
blocks and their actual definitions are in the block library.

•**Stateflow charts:** Models can contain Stateflow charts, which are
embedded in an MDL file.