How do I write a package?

ASCII/Text editor

Packages are ASCII/Text files that contain InputForm Mathematica commands. Comments can be included inside (* and *).

Mathematica menu command File > Save As Special > Package Format

This saves a notebook as a package. All input cells that are initialization cells will be included in the package. All other cells will be saved as comments. You can set the Initialization Cell property for a cell with the following menu command.

Cell > Cell Properties > Initialization Cell

You can also use the Option Inspector, which can be accessed via Format > Option Inspector. Please see the following FAQ for more information about the Option Inspector.

http://support.wolfram.com/mathematica/interface/options/inspector.html

You can set the option in the Option Inspector by selecting the following menu command.

Cell Options > Evaluation Options > Initialization Cell > True

AutoSave package

When saving a notebook with initialization cells, Mathematica may ask if you want to create an AutoSave package, depending on the settings of the following two options.

Notebook Options > Evaluation Options > InitializationCellWarning

Notebook Options > Evaluation Options > InitializationCellEvaluation

If an AutoSave package is created, all initialization cells are saved in the package. All other cells are omitted. A special header is also added at the beginning of the package.