Glossary

Buffers, Windows, Tabs

Buffer    An in-memory representation of a document
          May not correspond to that file "on disk"
          A buffer is a file loaded into memory for editing
          The original file remains unchanged until you write the buffer to the file

Window    A viewport on a buffer
          One buffer can have many windows (many viewports)
          When we do :q, we are actually quitting the current WINDOW


Tab Page  A collection of windows

Tab       Another tab in the terminal
          Not a Vim feature, strictly speaking

Example: Terminal Tabs vs Vim Tab Page

• there are 2 terminal tabs open
• the focused tab is split into a Vim Tab Page (described below), and another command prompt

Example: a Tab Page

• there are 3 windows open
• "Window 1" and "Window 2" are windows (viewports) on the same BUFFER (for file-1.md)
• "Window 3" is a window (viewport) on another BUFFER (for file-2.md)

Buffer States

1. Active     :buffers shows 'a'
2. Hidden     :buffers shows 'h'
3. Inactive   :buffers shows ' '

Modes

Normal Mode         the characters typed are executed as commands
Insert Mode    i    the characters typed are inserted as text
Replace Mode   r    the characters typed are inserted as text, replacing existing text
Visual Mode    v    the motion commands typed create a highlighted selection
Command Mode   :    the characters typed appear in the Command Line at the bottom of the window

Variables

Variables hold values for various settings in a system.

System Environment Variables

These variables are global to a computer system [170926]

$HOME         Full path to home directory

$TERM         Type of terminal
              xterm-256color
              xterm (probably limited to 8 colors)

We echo these in Vim Command Mode by referencing them with &:

Example: echo the current working directory

:ec &pwd

Vim Environment Variables

These variables are scoped with the Vim environment [170926] They are only accessible within Vim.

$VIM          Full path to where Vim is installed

$MYVIMRC      Full path to .vimrc file (if .vimrc exists)
              Empty is no .vimrc

Vim Options

Options are special internal variables and switches in Vim.

They can be set to achieve special effects.

We change options with the keyword set.

We inspect options by appending "?"

:set              Show all options that differ from their default value
:set number?      Show current value of option
:set number       Toggle option: set, switch it on; Number/String option: show value
:set number!      Set current value to toggled value (invert)
:set no{number}   Set option to off
:set {number}&    Set option to default value

:set pokemon?     E518: Unknown option: pokemon
                  "pokemon" is not a Vim option

:set number=30    E474: Invalid argument: number=yes
                  "30" is not a valid value for the option "number"

Vim Variables

These "regular" variables are also scoped with the Vim environment [170910]

They are only accessible within Vim.

Variables hold values for various settings / options. They are used by the user and plugins.

We change variables with the keyword let.

We inspect variables with :echo

:let {var}={value}    Create variable
:unlet {var}          Remove variable

Prefixes (and their SCOPE)
g: global-variable    Global scope
b: buffer-variable    Local scope - to the current buffer
w: window-variable    Local scope - to the current window
t: tabpage-variable   Local scope - to the current tab page
l: local-variable     Local scope - to a function
s: script-variable    Local scope - to a |:source|'ed Vim script
a: function-argument  Function scope - only accessible inside a function
v: vim-variable       Global scope, pre-defined by Vim

Note: If the namespace is not specified, then the global namespace is used

Examples:

:let pokemon=1000     Create global variable "pokemon", and assign it the value 1000
:echo pokemon         1000
:echo g:pokemon       1000
:echo w:pokemon       E121: Undefined variable: w:pokemon
                      E15: Invalid expression: w:pokemon

:let w:pokemon=2      Create a local variable "pokemon", scoped to the current window
:echo pokemon         1000 (the global variable)
:echo w:pokemon       2 (the window variable)

:echo syntastic_check_on_open       "1" will print out in the Command Line (it is "ON")
:echo g:syntastic_check_on_open     same as :echo syntastic_check_on_open
:echo g:syn<Tab>                    Remember that we can always perform Tab Completion