Registers

Emacs registers are compartments where you can save text, rectangles, positions, and other things for later use. Once you save text or a rectangle in a register, you can copy it into the buffer once, or many times; once you save a position in a register, you can jump back to that position once, or many times.

Each register has a name that consists of a single character, which we will denote by r; r can be a letter (such as ‘a’) or a number (such as ‘1’); case matters, so register ‘a’ is not the same as register ‘A’.

A register can store a position, a piece of text, a rectangle, a number, a window configuration, or a file name, but only one thing at any given time. Whatever you store in a register remains there until you store something else in that register. To see what register r contains, use M-x view-register

Type	How to save	How to use	Other useful command
Position	C-x r <SPC> r	jump: C-x r j r
Text	C-x r s r	insert: C-x r i r	m-x append-toregister <RET> r; m-x prepend-to-register <RET> r
Rectangle	C-x r r r	insert: C-x r i r
Window Config	C-x r w r	restore: C-x r j r	save all frame's window: C-x r f x
Number	C-u number C-x r n r	insert: C-x r i r	increment: C-x r + r
File	(set-register ?z '(fine . name))	jump: C-x r j r

Bookmark

Bookmark can be thought register with a long name and surviving between Emacs session.