Exit code 0 : Setup was successfully run to completion or the /HELP or /? command line parameter was used.

Exit code 1 : Setup failed to initialize.

Exit code 2 : The user clicked Cancel in the wizard before the actual installation started, or chose “No” on the opening “This will install…” message box.

Exit code 3 : A fatal error occurred while preparing to move to the next installation phase (for example, from displaying the pre-installation wizard pages to the actual installation process). This should never happen except under the most unusual of circumstances, such as running out of memory or Windows resources.

Exit code 4 : A fatal error occurred during the actual installation process.

Note: Errors that cause an Abort-Retry-Ignore box to be displayed are not fatal errors. If the user chooses Abort at such a message box, exit code 5 will be returned.

Exit code 5 : The user clicked Cancel during the actual installation process, or chose Abort at an Abort-Retry-Ignore box.

Exit code 7 : The Preparing to Install stage determined that Setup cannot proceed with installation. (First introduced in Inno Setup 5.4.1.)

Exit code 8 : The Preparing to Install stage determined that Setup cannot proceed with installation, and that the system needs to be restarted in order to correct the problem. (First introduced in Inno Setup 5.4.1.)

Before returning an exit code of 1, 3, 4, 7, or 8, an error message explaining the problem will normally be displayed.