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.
 Naming convention
There are 62 registers, each with a single character for a name:
- from a to z
- from A to Z, different from a to z
- from 0 to 9
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.
 How to use
|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 r|
|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|
- To see what register r contains, use M-x view-register
Bookmarks can be thought as register with a long name and surviving between Emacs session.