A handful of command line switches are processed by the VM and not the library. They control low-level features.

-i=image	Specifies the image file to use; see Images
-datastack=n	Datastack size, kilobytes
-retainstack=n	Retainstack size, kilobytes
-callstack=n	Callstack size, kilobytes
-callbacks=n	Callback heap size, kilobytes
-young=n	Size of youngest generation (0), megabytes
-aging=n	Size of aging generation (1), megabytes
-tenured=n	Size of oldest generation (2), megabytes
-codeheap=n	Code heap size, megabytes
-pic=n	Maximum inline cache size. Setting of 0 disables inline caching, >= 1 enables polymorphic inline caching
-fep	enter low-level debbugger, aka fep mode immediately
-no-signals	turn off OS signal handling
-console	open console if possible

If an -i= switch is not present, the default image file is used, which is usually a file named factor.image in the same directory as the Factor executable.