Thinking Macromodularly

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Copyright © 2025 Michael Herman (Bindloss, Alberta, Canada) – Creative Commons Attribution-ShareAlike 4.0 International Public License

The term “macromodular” generally refers to something composed of large, self-contained modules that can be combined or interchanged within a broader system.

Why Macromodular?

The amount of logically irrelevent engineering detail inherent in the design and construction of a computer system is great. As a result, the task of creating a system based on the use of present techniques is so difficult and time-consuming that the number of different systems that can be put into use for evaluation and study by any one group of workers is small. This is unfortunate as we are thereby denied the opportunity to develop that insight into logical organization which can grow out of a working familiarity with many diverse forms. What is needed is a set of relatively simple, easily inter-connected modules from which working systems can be readily assembled for evaluation and study. With such a set, both the designer and user would be able to try out potentially powerful and novel structures on a very large scale, adjusting and improving the systems as needed. Once a design has been realized and its value established, it could then be reworked into tighter engineering form for maximum efficiency and for production by automatic wiring and fabrication techniques, and the experimental units made available for further studies or returned to “inventory” in the manner proposed by Estrin.
Macromodular computer systems. Wesley Clark. 1967.

“Macromodular” is used in several contexts, each with a slightly different nuance.

1. Systems Design / Engineering

Meaning: A macromodular system is built from major components (modules) that can operate semi-independently but connect through defined interfaces.
Example: In aerospace or manufacturing, a rocket might be designed in macromodules — propulsion, guidance, payload — each built and tested separately, then integrated.
Contrast:
Modular → small, interchangeable units.
Macromodular → large, complex modules, often representing entire subsystems.

2. Software Architecture

Meaning: A macromodular architecture organizes codebases into large, cohesive components (e.g., microservices clusters or bounded contexts) rather than granular micro-modules.
Example: A company might have a “macromodule” for payments, another for user management, each encompassing many smaller internal modules.
Benefit: Easier maintainability and clearer ownership boundaries than hyper-granular microservices.

3. Biological or Cognitive Science (less common)

Sometimes used metaphorically to describe large functional units in a system — e.g., macromodular organization of the brain (sets of modules handling high-level tasks like perception or language).

In short: Macromodular = modular at a higher level of aggregation. It emphasizes large-scale modularity — balancing specialization and integration.

The term “macromodular systems” refers to systems composed of large, well-defined, interoperable modules that can be independently developed, maintained, and replaced, yet integrate seamlessly into a larger architecture. It’s an evolution of modular design thinking—scaling up modularity from components or microservices to system-level modules that encapsulate significant functionality or subsystems.

Resources

1. Organization of computer systems: the fixed plus variable structure computer. Gerald Estrin. 1960.
2. Macromodular computer systems. Wesley Clark. 1967.
3. Logical design of macromodules, Mishell J. Stucki et all. 1967.

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