Vi filename...
Text editor with the following commands (in command mode, unless preceded by a :)

a	Add text
cc	Substitute a line with a string <enters insert mode>
cw	Substitute, or change, a word with a string <enters insert mode>
dd	Delete the entire line the cursor is on
dw	Delete the word, or portion of the word, under and after the cursor
h	Move left, or "west", one character
i	Mnsert text under the cursor <enters insert mode>
j	Move down, or "south", one line
k	Move up, or "north", one line
l	Move right, or "east", one character
o	Insert text on a new blank line after the current line <enters insert mode>
O	Insert text on a new blank line before the current line <enters insert mode>
s	Substitute a character with a string
x	Delete the character under the cursor
:q	Quit vi
:q!	Quit vi, without writing changes
:w	Save, or write a file