Where do permanently deleted files go on computers?

Short answer there still there, they don't go anywhere

When you delete a file, you just change a pointer to the new address on your hard disk. Pointers are a special type of data that points to the location (Track/Cylinder/Sector of the hard drive) where the actual file is stored. Large files are usually stored in multiple locations. When you open a file, the hard drive follows the pointer to present the data.

The file is never erased; it is present physically on your hard disk. But the address where the file is located is made available for the next read/write operation.

You can get those files back using special software unless the location has been overwritten. Although, overwriting doesn’t guarantee that your files are gone forever. Organized criminals in Ghana have managed to recover confidential data from dumped electronic wastes. So if you are working for any secret agency, it’s better to destroy your hard disk rather than throwing it away.

Well, technically files never get deleted from your system.

Explanation:

When you delete a file, Windows (and some other operating systems) removes the pointer and marks the sectors containing the file’s data as available. From the systems P.O.V the file is deleted, and Space is marked as free in your Hard drive.

This is the reason why you can recover your file from the sectors containing the data until Windows actually writes new data over them

( Recuva is a good example of a recovery tool)

If you're wondering why the hell it just doesn't erase the files and get them over with ! well, it’s actually pretty simple.

Deleting a file’s pointer and marking its space as available is an extremely fast operation. In contrast, actually erasing a file by overwriting its data takes significantly longer.

For example, if you’re deleting a 10 GB file, that would be near-instantaneous. To actually erase the file’s contents, it may take several minutes – just as long as if you were writing 10 gigabytes of data to your hard drive.

To increase performance and save time, Windows and other operating systems don’t erase a file’s contents when it’s deleted.

it would be c. predictability