updated README.md

Hugh Barney 2017-03-26 18:18:04 +01:00
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#Zep Emacs
# Zep Emacs
Smallest usable Editor in less than 800 lines of C.
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> A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away.
> -- <cite>Antoine de Saint-Exupery</cite>
##Goals of Zep Emacs
## Goals of Zep Emacs
* Provide just enough editing features to be able to make small changes to files
* Smallest code footprint to demonstrate the buffer editor concept without the distraction of more advanced editor features.
* Be easy to understand without requiring extensive study (to encourage further experimentation).
##Why the name Zep ?
## Why the name Zep ?
The small Emacs naming scheme appears to use sub-unit prefixes in decending order with each further reduction of functionality. The Nano and Pico Emacs editors have been around for a while.
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Zep has the smallest possible feature set to make a viable file editor. Zep supports basic movement around the file, character insertion, deletion, backspace, line deletion, cut, copy, paste and the ability to search for a text string. Although Zep uses a subset of the Emacs keyboard command set; it cant really be considered to be an Emacs in that it does not support the editing of multiple files in multiple windows.
## Derivation
Femto, Atto, Zepto and Zep are based on the public domain code of Anthony Howe's editor (commonly known as Anthony's Editor or AE, [2]). Rather than representing a file as a linked list of lines, the AE Editor uses the concept of a Buffer-Gap [4,5,6]. A Buffer-Gap editor stores the file in a single piece of contiguous memory with some extra unused space known as the buffer gap. On character insertion and deletion the gap is first moved to the current point. A character deletion then extends the gap by moving the gap pointer back by 1 OR the gap is reduced by 1 when a character is inserted. The Buffer-Gap technique is elegant and significantly reduces the amount of code required to load a file, modify it and redraw the display. The proof of this is seen when you consider that Atto supports almost the same command set that Pico supports, but Pico requires almost 17 times the amount of code.
##Comparisons with Other Emacs Implementations
## Comparisons with Other Emacs Implementations
Editor Binary BinSize KLOC Files
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ue3.10 uemacs 171664 52.4K 16
GNUEmacs emacs 14632920 358.0k 186
##Starting Zep
## Starting Zep
Zep can only open one file at a time. The filename to edit must be specified on the command line.
$ zep filename
##Zep Key Bindings
## Zep Key Bindings
C-A begining-of-line
C-B backward-character
C-D delete-char
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Down Move to the next line
Backspace delete caharacter on the left
### Searching
C-S enters the search prompt, where you type the search string
BACKSPACE - will reduce the search string, any other character will extend it
C-S at the search prompt will search forward, will wrap at end of the buffer
ESC will escape from the search prompt and return to the point of the match
C-G abort the search and return to point before the search started
###Copying and moving
### Copying and moving
C-<spacebar> Set mark at current position
^W Delete region
^Y Yank back kill buffer at cursor
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2. Delete it (with ^W) or copy it (with M-W) into the kill buffer.
3. Move the cursor to the desired location and yank it back (with ^Y).
## Copying
Zep is released to the public domain.
hughbarney AT gmail.com 2017
## References
[1] Perfect Emacs - https://github.com/hughbarney/pEmacs
[2] Anthony's Editor - https://github.com/hughbarney/Anthony-s-Editor
[3] MG - https://github.com/rzalamena/mg