VIM Useful Commands

a: Append text after the cursor.  
i: Insert text before the cursor.
o: Begin a new line below the cursor and insert text.

x :  Delete character under and after the cursor.
dd: Delete the current line.
d0: Delete everything from where your cursor is to the beginning of the line.
dG: Delete all lines.
ctrl + w: Delete a word near the cursor(a string sperate by spaces).
ctrl + u: Delete all the text that has been typed on the command line.

:%s[ubstitute]/{search_text}/{replace_text}/<command_flag>
[eg]: :%s/YYC/yyc/gc
c: Confirm each substitution.
i: Ignore case for the pattern.
g: Replace all occurrences in the line. Without this arugument, 
   replacement occurs only for the first occurrence in each line.

yy: Yank the current line [into register x]. 
p : Put the text [from register x] after the cursor.

u: undo changes.
.: Repeat last change.

    k
h       l
    j
0    : To the first character of the line (exclusive).
Home : To the first character of the line (exclusive).
^    : To the first non-blank character of the line.
$/End: To the end of the line.
gg   : places the cursor at the start of the file.
G    : Places the cursor at the end of the file.
123G : Go to the specific line number.
w    : Places the cursor at the next word.
b    : Places the cursor backwards to the beginning of the current or previous word.
e    : Places the cursor backwards to the end of the current or next word.
ctrl + a: To the first character of the line(ahead).
ctrl + e: To the end of the line.

/{pattern}: Search forward for the occurrence of {pattern}.

guu: lowercase line.
gUU: uppercase line.
ctrl + -: Switch the current directory to the last directory.

sp  file_name: Open another window horizontally.
vsp file_name: Open another window vertically.
ctrl + w + h : Move window to the left.
ctrl + w + j : Move window down.
ctrl + w + k : Move window up.
ctrl + w + l : Move window to the right.