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Typo: vrtual -> virtual (#518)

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Changed in blog post "Paging Introduction".
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Matthew Klein
2019-01-14 09:35:19 -06:00
committed by Philipp Oppermann
parent c478c7a90e
commit f28bed6436
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blog/content/second-edition/posts/09-paging-introduction/index.md
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@@ -45,7 +45,7 @@ By modifying the memory addresses before the actual access, segmentation already
The idea behind virtual memory is to abstract away the memory addresses from the underlying physical storage device. Instead of directly accessing the storage device, a translation step is performed first. For segmentation, the translation step is to add the offset address of the active segment. Imagine a program accessing memory address `0x1234000` in a segment with offset `0x1111000`: The address that is really accessed is `0x2345000`. The idea behind virtual memory is to abstract away the memory addresses from the underlying physical storage device. Instead of directly accessing the storage device, a translation step is performed first. For segmentation, the translation step is to add the offset address of the active segment. Imagine a program accessing memory address `0x1234000` in a segment with offset `0x1111000`: The address that is really accessed is `0x2345000`.
To differentiate the two address types, addresses before the translation are called _virtual_ and addresses after the translation are called _physical_. One important difference between these two kinds of addresses is that physical addresses are unique and always refer to the same, distinct memory location. Virtual addresses on the other hand depend on the translation function. It is entirely possible that two different vrtual addresses refer to the same physical address. Also, identical virtual addresses can refer to different physical addresses when they use different translation functions. To differentiate the two address types, addresses before the translation are called _virtual_ and addresses after the translation are called _physical_. One important difference between these two kinds of addresses is that physical addresses are unique and always refer to the same, distinct memory location. Virtual addresses on the other hand depend on the translation function. It is entirely possible that two different virtual addresses refer to the same physical address. Also, identical virtual addresses can refer to different physical addresses when they use different translation functions.
An example where this property is useful is running the same program twice in parallel: An example where this property is useful is running the same program twice in parallel: