string replacement

Sometimes you want to replace one string with another. This is done with the ex command "s". The form of the replacement is :

: line_range s/old/new/g

ex ( replace foo with bar from line 10 to 20 ) :

:10,20s/foo/bar/g

You can use visual mode to select the lines, when you type the colon to start the command it will use symbols for the visual line range.