Specifically here I am talking about the concept of “re-use”. That is, the ability to write a bunch of code that does a “thing” and use that more than once, without significant modification.
Modularity is a much bigger concept, related to the engineering of large software systems. These days, “micro-services” is one way that people achieve modularity, but in the old days it was needed for many of the same reasons, but inside the monolith. The overall solution is composed of blocks living at different layers.
Re-use also exists inside modules, of course, by using functions or composition or — shudder — inheritance of code.
Modular programming has value as soon as more than one team needs to work on something. As it’s impossible to predict the future, my opinion is that it always has value to structure a code-base in this way.
Modularity is a much bigger concept, related to the engineering of large software systems. These days, “micro-services” is one way that people achieve modularity, but in the old days it was needed for many of the same reasons, but inside the monolith. The overall solution is composed of blocks living at different layers.
Re-use also exists inside modules, of course, by using functions or composition or — shudder — inheritance of code.
Modular programming has value as soon as more than one team needs to work on something. As it’s impossible to predict the future, my opinion is that it always has value to structure a code-base in this way.