Initialization files are used by MESS to define easily the plethora of directives that affect the emulation of a system. These files have the .ini extension and must not be confused with the configuration files, which serve a different purpose.

The most important of these files is, not surprisingly, named mess.ini. However, the user can define a hierarchy of .ini files in order to restrict some options to a subset of the available drivers.

The format of an initialization file is very simple: each line can be an option, a blank or a comment (beginning with #).

Each option accept a parameter (which con be an integer, a float, a string or a path) and has a direct correspondence with a command-line switch - the following line into an .ini file:

frameskip 12

is equivalent to running MESS this way:

mess -frameskip 12

The only exception to this rule is constituted by the boolean (i.e. ONOFF) options. These options accept a numeric parameter (where 1 means ON and 0 means OFF**) when used in the .ini file, but are prefixed by the string no when used on the command line. Thus the line:

autoframeskip 0

into an .ini file is equivalent to:

mess -noautoframeskip

from the command line.