On modern OSs, files get mapped into RAM, which is a fancy way of saying “it can stay on disk, but it can also be cached in RAM, but the unmodified parts can get discarded out of cache at any moment, and any changes go first to RAM, then get written to disk at some later time”.
The apps also use buffers to hold data, and one of the largest buffers is for the canvas or window display buffer. These have to use actual RAM while the app is running; you can only swap them out to swap/pagefile if you suspend the app… which is doable, but rarely done… otherwise they’ll get swapped back in, the moment the app needs them (which usually is all the time… but some buffers might stay mostly swapped out some of the time).
There is also RAM compression going on (at least on Windows), that can keep mostly empty and/or rarely used buffers all the time “in RAM”, but taking just a fraction of the space.
Yes and no.
On modern OSs, files get mapped into RAM, which is a fancy way of saying “it can stay on disk, but it can also be cached in RAM, but the unmodified parts can get discarded out of cache at any moment, and any changes go first to RAM, then get written to disk at some later time”.
The apps also use buffers to hold data, and one of the largest buffers is for the canvas or window display buffer. These have to use actual RAM while the app is running; you can only swap them out to swap/pagefile if you suspend the app… which is doable, but rarely done… otherwise they’ll get swapped back in, the moment the app needs them (which usually is all the time… but some buffers might stay mostly swapped out some of the time).
There is also RAM compression going on (at least on Windows), that can keep mostly empty and/or rarely used buffers all the time “in RAM”, but taking just a fraction of the space.