How does an uninitiliazed variable get a garbage value?

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The garbage value is not assigned, rather the value is already there. When you allocate a variable you are reserving a piece of memory – until you overwrite it that memory will contain whatever “random” information was there before.

As a metaphor, think of allocating a variable like buying a piece of land – until you do something with it (like build a house) the land will just have whatever trash was already sitting there (like an old crumbling house).

Some languages will automatically fill newly allocated variables with zeros – this takes time to do. In more “do-it-yourself” languages like C this extra behavoir is not guarenteed (though on some systems memory is cleared regardless of language, for example as a security measure)

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