This book offers an in-depth insight into the general-purpose finite
element program MSC Marc, which is distributed by MSC Software
Corporation. It is a specialized program for nonlinear problems
(implicit solver) which is common in academia and industry. The primary
goal of this book is to provide a comprehensive introduction to a
special feature of this software: the user can write user-subroutines in
the programming language Fortran, which is the language of all classical
finite element packages. This subroutine feature allows the user to
replace certain modules of the core code and to implement new features
such as constitutive laws or new elements. Thus, the functionality of
commercial codes ('black box') can easily be extended by linking user
written code to the main core of the program. This feature allows to
take advantage of a commercial software package with the flexibility of
a 'semi-open' code.