The items below INITEX are specified by the format_files parameter.
The Default config file sets the formats to
LaTeX, AMSTeX and Plain.
The current format is indicated by a tick and will be the one used when you
typeset a file, although this will be overridden if the first line of the
file starts with ``%&format''.
To change the current format, simply select a different format item.
automatically ticks the first format found when loading a
config file containing format_files, so it's a good idea to place
your preferred format first.