When **GNU Archimedes** saves the various solution outputs, it have to know in which format to do it. This is specified by the user in the following way, in the input file

OUTPUTFORMAT formattypewhere

**GNUPLOT**. This sets that the output files will finish by the extension*xyz*which means that the file will be in the following format**MESH**. The*MESH*format is a little bit more complex than the*GNUPLOT*one. In this case, we have a file which describes the mesh and another which describes the solution on that mesh.

Concerning the mesh file, it have a file structure like the followingMeshVersionFormatted 1 Dimension 2 Vertices number of vertices x1 y1 0 x2 y1 0 x3 y1 0 ... xn y1 0 ... xn yn 0 Quadrilaterals number of quadrilaterals v1_1 v2_1 v3_1 v4_1 0 v1_2 v2_2 v3_2 v4_2 0 ... v1_N v2_N v3_N v4_N 0

Concerning the file for the solution on the mesh, the file have the following structure

2 1 number of vertices 2 solution on the 1-st vertex solution on the 2-nd vertex solution on the 3-th vertex solution on the 4-th vertex ... solution on the last vertex

This kind of format is becoming very popular in the scientifical computation community, that is why the author have reputed important to implement it in**GNU Archimedes**.