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How do patches and service packs work?

How do patches or service packs work? I do not know how to explain my question, but I will try

Take Windows for example. It has files that collectively consume 100 MB. Now one service pack (maybe 300 MB in size) updates the entire Windows OS.

Similarly, I saw updates for software products such as adobe reader, etc. In all of these cases, the core exe is much larger than the upgrade. How does this process work? If the main file refers to any dependency files, and if the update changes version or size. Will it affect exe?

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Patches and service packs usually only need to update the main shared libraries of the system. These libraries are replaced or corrected from a compressed archive, therefore, their size. After updating the libraries, the rest of the OS software may continue to use new versions.

Applications are currently designed for modular operation and the use of external libraries that can be easily updated. Sometimes the main application or any media used does not need to be replaced, but only a modified library.

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To supplement the previous answers, on the same day that the file size really mattered, some patches were delivered as binary differences, that is, the patch itself was executable, which knew which files needed to be changed, and how, and actually changed only a certain part of zeros and units of files, locally, instead of completely replacing files.

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The following URL may be of interest to you, knowing the architecture.

http://msdn.microsoft.com/en-us/library/aa387291(VS.85).aspx

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Patches (also called deltas) are just the differences between the two files. If only a few bytes of a 1GB file are changed, the patch will have only a few bytes of size. For text files, diff is used for xdelta binaries or the like. Service packs are collections of patches.

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