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Chapter 3: Free Format Input Up Chapter 3: Free Format Input Subsection 3.1.1: Format Specification Versions

## 3.1 Free Format Overview

The free format organizes the FEBio input data into hierarchical XML elements. The root element is called febio_spec. This root element also defines the format version number (Note that FEBio and the input format specification follow different version numberings). This document describes version 3.0 of the FEBio specification [F]  [F] FEBio continues to read some older formats, but they are considered to be obsolete. (see Section 3.1.1↓ below for more details on the different input specification formats). The root element will therefore be defined as follows:
<febio_spec version="3.0">
<!-- contents of file -->
</febio_spec>

The different sections introduced in this chapter are child elements of this root element. The following sections are currently defined:
Module defines the physics module for solving the model.
Control specifies control and solver parameters.
Globals Defines the global variables in the model
Material Specifies the materials used in the problem and the material parameters.
Mesh Defines the mesh of the problem, including nodal coordinates and element connectivity.
MeshDomains Assigns materials and other formulation attributes to element sets.
MeshData Defines element, facet, edge or nodal data that can be mapped to material parameters or certain boundary conditions and loads.
Initial Defines initial conditions for dynamic problems, such as initial velocities, and for transient quasi-static problems.
Boundary Defines the boundary conditions that are applied on the geometry.