Data structure
The main concept of 4ti2 remains the same: a project is defined via a file 'foo' containing the problem matrix. Related sets such as Graver basis or Markov basis are put into 'foo.gra' and 'foo.mar', respectively.

Input files and output files usually contain a matrix or a list of vectors (written as a matrix) in a standard encoding such as

2 4
1 1 1 1
1 2 3 4

There are only few exceptions, for example in a file 'foo.vars' containing user specified variable names:

3
a b x