What is Emacs???

Emacs is a text editor — a computer application which allows users to create, modify, and save text files on a computer's file system. Emacs is a self-documenting, customizable, extensible, real-time display editor.

Emacs is classified as a display editor because it displays the contents of a file as its typed rather than requiring a special command to view the contents. It is real-time because the screen updates as each character is typed. Changes can be seen immediately as they are input. We call Emacs self-documenting since its complete documentation is built-in and is available at any time with just a keystroke (C-h). Emacs is customizable and extensible because commands can be re-mapped to different keystrokes, and new commands can be created and added to its basic functionality.

Because the source to GNU Emacs is freely-distributed, its flexibility is further enhanced. Emacs is found on a variety of operating systems and architectures, most notably on UNIX and Windoze machines. The particular variety of Emacs we will be discussing in this document is GNU Emacs (version 19), a widely-installed distribution of Emacs from the Free Software Foundation.

How Emacs Interacts with Files

Emacs, as with editors in general, does not directly access a file's contents. Instead, Emacs copies the contents of the file into a buffer. A buffer is a temporary work area where Emacs allows you to edit a text file. The real file is left untouched as a backup until Emacs is given the explicit command to save the buffer, at which time the changes are saved permanently. Emacs also supports the "version" capability of the operating system on which it resides. For instance, on UNIX, the previous edition of a file exists as the filename appended with a tilde (~).

Before getting started...

• It is best to work through this tutorial with emacs running in a separate window. If you are on an X-term, then type emacs & at the UNIX prompt to start emacs.
• The sample file used in the labs can be copied to your local directory from the following link: source_lab01_sample.txt. Please download this file to your home directory and rename it to sample.txt.
• You may wish to view/print the Emacs Commands Reference before working through the lab.
• The Control Key
  Control characters are formed by pressing and holding down the keyboard key labeled CONTROL then pressing and releasing another character. The CONTROL key is denoted by the capital letter C. A control sequence, such as C-g, is considered one keystroke. Here is an example of a control sequence: C-g. This means press and hold the CONTROL key and type a g character. Do not hold down the g for an extended period (i.e., don't keep it pressed down).
• The Meta Key
  The meta-key is denoted in both this handout and most Emacs references by a capital M. Although it can be defined to be just about any key, we have chosen the ESCAPE key since it is available on most keyboards. The ESCAPE key is usually labeled as ESC on the keyboard. Here is an example of a meta command: M-x. This means press and release the meta key (which we have defined to be the ESC key) and then type an x character. Do not hold down the meta key, this will inadvertantly invoke a lisp evaluation function. If this happens by mistake, press C-g to exit.

The Emacs display consists of several parts: the text window, mini-buffer (also called the echo area), mode line, menu bar (X version only) and the frame. The Emacs image on your particular screen might not look exactly like the diagram below because of your particular environment. The text window is the area which displays the current section of the open buffer. The last line of the text window is called the mode line and is displayed in reverse video.

Directly underneath the mode line, on the last line of the entire Emacs display, is the mini-buffer. When the first keystroke of a key sequence that requires a second keystroke has been entered, the cursor moves to the mini-buffer to prompt for the rest of the command. To cancel a command in progress, type C-g.

The entire Emacs display is contained within a frame.

Getting Started: Creating and saving a file

1. Start up Emacs with a new file called test by entering emacs test from the UNIX prompt and pressing the RETURN KEY.
   When you are using Emacs in an X environment, it may be more convienent to put the Emacs session into the background by appending an ampersand (&) when starting Emacs. For example, emacs test & invokes an Emacs frame and allows you to continue entering additional commands at the UNIX prompt, such as g++ source.cpp -o run_me.exe.
2. An empty Emacs buffer will appear on your screen. Type a sentence into the text buffer and save it with the command C-x C-s.
3. Enter C-x C-c to exit Emacs.

The cursor, sometimes called a point, is the point of insertion and the point of deletion. In other words, when characters are typed they appear at the location of the cursor and when the backspace key is typed, characters will disappear from the location immediately left of the cursor.

To insert and delete characters, it is necessary to move the cursor to the desired location in the text buffer. The following lab utilizes the most commonly used commands for changing the location of the cursor.

Edit the file sample.txt by entering emacs sample.txt & at the UNIX prompt and press the RETURN KEY. Note that this will only work if you have already copied the file sample.txt into your directory, as per above.

Practice moving forward and backward, from one line to the next, and to the beginning and end of the buffer. Use the table of commands below:

         Description              Lisp Function Name

    C-f  next character           forward-char
    C-b  previous character       backward-char
    C-n  next line                next-line
    C-p  previous line            previous-line
    C-e  end of line              end-of-line
    C-a  beginning of line        beginning-of-line
    M->  end of buffer            end-of-buffer
    M-<  beginning of buffer      beginning-of-buffer
    C-v  forward one screen       scroll-up
    M-v  back one screen          scroll-down

This lab shows how to kill (delete) small amounts of text near the cursor as well as larger amounts of text, such as words, lines, and paragraphs, by defining regions. Regions are defined by setting invisible marks in the buffer. All killed text is placed into a buffer called the kill ring. The kill ring is a record of all your previous kills.

Text which has been killed is saved in the kill ring as a block. A block might consist of a single character, or any sized region. Note that subsequent kills with no intervening insert commands will be saved as one block. For instance, multiple C-k (kill-line) commands will save all of the killed text as one single block in the kill ring. The kill ring can be accessed as a method to bring killed text back into your buffer (see "Moving Text & Undoing Changes").

For a summary of kill commands see the Lab Command Summary. Now try the lab, which involves killing text:

• Move to the end of a line of text and use the DELETE key to kill text back to the beginning of the line.
• Delete a line of text by killing the characters one at a time with C-d. This command kills the character at the cursor's location.
• Kill text to the right of the cursor one word at a time with M-d.
• Move to the end of a line and kill to the left of the cursor one word at a time with M-delete.
• Move to the third word of a line and kill to the end of a line by using C-k. This command kills from the cursor's location to the end of the line.
• Mark and kill a region in the buffer. Mark the beginning of a region using C-space. Next move the cursor after the last character in the region and write it to the kill ring with the command C-w.

Lab Command Summary