What is the difference between “File scope” and “program scope”

Question

A variable declared globally is said to having program scope
A variable declared globally with static keyword is said to have file scope.

For example:

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Answer 1

C programs can be written in several files, which are combined by a linker into the final execution. If your entire program is in one file, then there is no difference. But in real-world complex software which includes the use of libraries of functions in distinct files, the difference is significant.