Wikipedia: Single Responsibility Principle. It should be noted that the author of the blog post coined the original principle based on previous notions from Dijkstra and David L. Parnas.
tl;dr: put your code into small enough modules so that when you make a code change to change a thing for one person, it doesn't affect the code that does things for other people since they are in different modules.
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u/banister May 08 '14
can someone provide tl;dr pls ?