按i在光标前插入字符，a在光标后追加字符

ctrl+d将光标下称半个窗口，按Ctrl+u将光标上移半个窗口

在输入模式下：ctrl+h删除字符，ctrl+u删除行，ctrl+w删除字

命令模式下，x删除字符，dw删除字，dd删除行

u表示撤销上一个操作

ctrl+r或输入命令:redo，表示重做

命令dw和i可以用一条命令cw（chang world）来实现。命令cw可以使用VIM进入输入模式

$ vim -r memo

:w memo2

可将文件另存

dw: delete current word, but first thing for this command is the cursor has to be the first character of the word.
d$: delete to the end of the line
0: move to the end of the line.
d3w: delete the 3 words after the cursor. d4w will delete 4 words
U: To undo all the changes on a line
p: put the line which deleted by command ‘dd‘ under the cursor line
r: Type rx to replace the character at the cursor with x
ce: To change until the end of a word, type ce
c$: Delete the context from cursor to the end of the line, and go the input mode
ctrl+g : To show your location in the file and the file status.
G: Go to the bottom of the file.
gg: To move you to the start of the file.
G: Type the number of the line you want to go and then G, this will go to the line you wann to go.

/: search for the phrase from forward
?: search for the phrase from backward
n: search the same phrase again, simple type n
N: search the same phrase in the opposite direction, type N
ctrl+o: To go back to where you came from. Repeat to go back further
ctrl+i: To go forward
%: to find a matching ),], or }. This is very useful in debugging a program with unmatched parentheses
:s/old/new/ to substitute ‘new‘ for ‘old‘, only change the first occurrence
:s/old/new/g to substitute ‘new‘ for ‘old‘, will change all the occurrences in the line
:%s/old/new/g to change every occurrence in the whole file
:%s/old/new/gc to find every occurrence in the whole file, with a prompt whether to substitute or not
o: to open a line below the cursor and place you in insert mode.
O: to open a line above the cursor and place you in insert mode.
a: to insert text AFTER the cursor
i: to insert text BEFORE the cursor
A: to insert text at the end of line
R: replace more than one character
r: replace one character of cursor position

copy and paste:
1. start visual mode with v and move the cursor to select the text you want to copy
2. Type y to yank(copy) the highlighted text.
3. Go to the position which you want to paste your text
4. Type p to put(paste) the text

set option:
:set number(set nu): show up line number
:set ic: set ignores case when searching or substitute
:set hls is: set lisearch and incsearch option
:set noic: disable ignoring case
if you want to ignore case for just one search command, user \c in the phrase: /youString\c

VIM