# Introduction

Many models require imported numerical data from external applications such as spreadsheets. Or, you may need to export numerical data from a model to another application. The software provides two basic mechanisms for importing and exporting data. First, you can manually import/export data via Copy and Paste operations. Second, you can establish active data links between a model and a file created by another application. Under Windows 95/98/NT/2000/XP operating systems, these links are created using Dynamic Data Exchange (DDE). Under the Macintosh operating system, linkages are created using Publish and Subscribe. This Chapter will outline the use of both manual import/export and active data linkages.