The [Code] section is an optional section that specifies a Pascal script. A Pascal script can be used to customize Setup or Uninstall in many ways. Note that creating a Pascal script is not easy and requires experience with Inno Setup and knowledge about programming in Pascal or at least a similar programming language.

The "Code*.iss" and "UninstallCode*.iss" files in the "Examples" subdirectory in your Inno Setup directory contain various example [Code] sections. Please study them carefully before trying to create your own Pascal script.

Note: to learn more the Pascal programming language you may find useful to refer to Marco Cantu's free Essential Pascal book. See http://www.marcocantu.com/epascal/.