A vertical file is a file in a special textual format which contains all texts of a corpus including metainformation. Each position (token, structure) is on a separate line with the metainformation (part of speech, lemma) in the next columns. An example of a vertical file:

A	DT	a-x
text	NN	text-n
corpus	NN	corpus-n
can	MD	can-x
consist	VV	consist-v
of	IN	of-i

note: 1st columns are tokens or structures, 2nd column part of speech tags, 3rd column lempos attribute