MITgcm-Configuration-Model.md

+The MITgcm configuration comprises of:
+- Selected packages
+- General configuration parameter
+- Features
+
+## Code configuration
+
+### Packages
+
+- **Packages** provide specific functionality for the model
+- **Package groups** are collections of commonly used packages which are defined in `pkg/pkg_groups`
+- Packages have dependencies which are defined in `pkg/pkg_depend`
+  - Essentially this is a simple feature model with dependencies and exclusions
+
+### SIZE_H
+
+- Model size setup
+- Located in `code/SIZE.h`
+
+### *_OPTIONS.h
+
+- Control features of packages
+- Global features are controlled in `code/CPP_OPTIONS.h`
+- Specific features are controlled in package related `<PKG>_OPTIONS.h` files
+
+## Input Data
+
+- Contains the input data files required to run an experiment
+- `input/data` namelist for parameterization
+- `input/data.pkg` namelist for the packages
+- `input/eedata` namelist for the execution environment setup
+- May also contain forcing data