Note
	This section is nearly finished but is still under development.

	Tip
	Only the commands that start with a colon (:) (which are from the ex line editor) require pressing Enter to be executed. All other commands in vi and Vim are executed immediately after they are entered. In addition, all vi and Vim commands are case-sensitive.

Vi (pronounced VEE-EYE)^[37] “was the first real screen-based editor for Unix systems.”^[38] It is present on all Unix and Unix-like operating systems (including Linux). Another frequently used text editor, GNU Emacs (discussed in Section 5.2, “GNU Emacs”), is usually (but not always) installed as well. You can start vi by typing vi or vi file_to_edit (such as vi lab0.c) at the prompt.

Vi is closely connected to the even older line-based text editor ex, whose commands begin with a colon (:). [reference! Also something (very) short about age/origin of vi.] In fact, you can start either editor from the command line and can switch between the two while using them. As can be seen from the tables below, vi users must know a few essential ex commands. However, a thorough coverage of ex is beyond the scope of this guide.

Since the original vi was a closed-source project,^[39] developers created their own clones of vi, adding new features along the way. One of the most popular of these clones is Vim (short for vi improved), created by Bram Moolenaar. Vim seems to be the standard version of vi on Linux machines, although other vi clones, such as elvis and vile, exist. However, the rest of this section will focus exclusively on Vim. Although Vim has much in common with the original vi and with the various vi clones, there are differences among them, including incompatibilities between Vim and vi. This guide will not cover those distinctions; anyone who is interested can check the references listed in the further reading section.

Vim is a modal editor that fundamentally has two modes: a normal (or command) mode for entering commands and an insert mode for entering and editing text. By comparison, modeless editors such as Emacs are always in insert mode, so that the characters you type always appear as text on the screen. As listed in Table 5.10, “Other modes in Vim”, Vim also includes a replace mode, which differs from insert mode in that any characters typed will overwrite existing characters in the buffer, as well as three types of visual modes, which allow for selecting text for cutting or copying.

	Tip
	You can return to normal mode at any time by pressing the Escape key.

[TODO - Importance of normal/command mode, operators/commands and motions/text-objects, delete vs. change vs. yank (and put?), etc.]

When vi was invented, the H, J, K, and L keys doubled as arrow keys, since there was no separate set of arrow keys on the keyboard. Thus vi and its clones still use those keys as arrow keys in the format shown in Table 5.1, “The Arrow Keys in Vim” below. Although the now-standard arrow keys work in Vim as expected, you may wish to try using the HJKL keys in their place, as you may find it faster to use them rather than having to reach to the arrow keys to use them.

To type a command like C-r, press the R key while holding down the Ctrl/Control key.

References to further reading on vi and Vim can be found in Section A.4.1, “More on vi and Vim”.