Free Body Problems

By background I am an Aerospace Engineer;(1) by starting in computational mathematics and CFD, and later physical modeling, I became a “programmer” through effort.(2) Engineers are taught to think of systems as Free-Body Diagrams, e.g. that the system can be understood as a sum of the input forces.


With software we think of the system through the Interface Control Document (ICD) and the system architecture. A common mistake for engineers who are working in programing is to treat an ICD like an FBD; as if it was the full summation of the system. The correct analogy is to look at the system architecture and ICD with the system call tree.


The primary or key observation should be that units of software are, more often than not, analogous to individual forces in your system. It is only in the summation of these units that you have the full system. The system architecture is the portion of the environment that defines when and where the calculations are performed.


  1. In truth my earliest “work” was as a programmer at age 8, writing the program “guess it”, where the computer would guess the number you had selected.
  2. Learning to write a program in C / Simulink is not the same thing as being a Computer Scientist, that is, when you start to think about the structure and format of your code / models. Unfortunately, there is often confusion as to what the roles of an engineer versus CS person should be in the development of software.

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