latex logs begin with
%&-line parsing enabled
What does it mean?
Some TeX engines (e.g. based on Web2C) have the feature that the format file can also be specified in the first line of the document, e.g.:
This specifies the format
In both cases the LaTeX format is used and PDF is generated.
From the manual page of TeX:
%& parsing is an option which allows one to indicate which TeX variant a particular file requires, e.g.,