How to get PageUp and PageDown to return to the exact same character?

Question

Because the default Ctrl-B/F or PageUp/Down behaviour usually leaves the cursor somewhere other than where it started, I remapped PageUp and PageDown in my .vimrc to simply move up/down 25 lines.

nnoremap <silent> <PageUp> 25<Up> 
nnoremap <silent> <PageDown> 25<Down>

But if I get to the top of the file the line number goes to 1 and so when I return down to near the original text it is now on the wrong line.

Is there some way to correct for this (perhaps some function for PageUp and PageDown that remembers when it could only go a lesser distance and so the first movement in the opposite direction also goes a lesser distance, or possibly some scheme where a marker is placed at the original spot... although I'd prefer not to have to remember to do that manually every time, just in case I may find myself needing it because I try to scroll too far).

I use Fedora 28 (but I'm pretty sure vi/vim under other systems had this problem of returning to a different line). Ctrl-B/F have the side effect of moving the cursor to the last/first line on the screen, so I often find the process of looking at something off the top of the screen means returning afterwards does not actually return me to the correct line; I have to hit up/down arrows a lot. And PageUp/Down keys are mapped to Ctrl-B/F so have this annoying feature. Using Ctrl-U/D or my simple workaround is usually better, except if I accidentally try to go too far... hence my question of a more general solution.

Answer 1

You can mark the current position of the cursor typing m followed by an alphabet in normal mode which is the register to store it. If you use ma to mark it, you can jump back to this position by `a or 'a. For more details, run :help mark in vim.

If you had used certain commands to navigate the documents, you can also have a look at :help jump-motions in vim.

As quoted there

A "jump" is one of the following commands: "'", "`", "G", "/", "?", "n", "N", "%", "(", ")", "[[", "]]", "{", "}", ":s", ":tag", "L", "M", "H" and the commands that start editing a new file. If you make the cursor "jump" with one of these commands, the position of the cursor before the jump is remembered. You can return to that position with the "''" and "``" command, unless the line containing that position was changed or deleted.

Answer 2

You could use Ctrl+O to go back to the previous positions instead of relying on the standard scrolling commands.