Compiler Mode

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The Free Pascal compiler will compile in a specific mode. Each mode dictates what syntax the compiler accepts as valid, and what it considers as invalid. The compiler mode can be set in the source code with the {$mode } compiler directive, or on the command line with the -M command line option.


  • Free Pascal: {$mode FPC}
    This is the original Free Pascal compiler mode. As of version 3, It is the default mode of the compiler, so it is not necessary to explicitly add this directive.
  • ISO 7185 Standard Pascal: {$mode ISO}
    The ISO 7185 standard compatibility mode. The ISO 7185 standard is also known as Standard Pascal.


As of version 2.3.1 of Free Pascal, the {$ModeSwitch} compiler directive has been added to allow features of a compiler mode to be selectively added to the current mode, effectively creating a custom mode. For example:

{$mode FPC}
{$ModeSwitch EXCEPTIONS}

Will add exception handling to the FPC compiler mode.

See also