Vi Editor basic user guide

vi is a screen-oriented text editor originally created for the Unix operating system.
Here are the few basic and necessary shortcuts to use vi editor effectively-

• '0'(zero) -move cursor to start of current line
• ':n' -move cursor to line n
• ':$' -move cursor to last line in file
• 'x' -delete single character under cursor
• 'dd' -delete entire current line
• 'dw' -delete the single word beginning with character under cursor
• 'yy' -copy (yank, cut) the current line into the buffer
• 'Nyy' -copy (yank, cut) the next N lines, including the current line, into the buffer
• 'p' -put (paste) the line(s) in the buffer into the text after the current line
• '/string' -search forward for occurrence of string in text
• '?string' -search backward 
• 'n'  -move to next occurrence of search string
• 'N'  -search for previous occurrence 
• 'u' -Undo last change
• 'ctrl + r'  - Redo 
• ':s/OLD/NEW/g'  -Replace OLD with NEW Globally (all) on current line
• ':%s/OLD/NEW/g'   -Replace OLD with NEW Every occurrence in file