#print
You can also change several lines, and you need not replace
lines with the same number of lines.  You can put any amount
of text between the 'c' command and the closing '.', and
you can remove any number of lines from the file by specifying
a range of addresses.  For example, 

   2,5c
   first
   second
   .
would replace the FOUR lines 2,3,4 and 5 of the file with TWO
new lines containing "first" and "second".  You can of course
use more complicated addresses involving $ and . if you wish.
This directory contains a file "oldrr".  Delete the last two
lines and replace them by a line reading

penn central

and write the new version on a file named "newrr".  Then use "diff"
to compare the old and new versions of the file.
Eventually, type "ready".
#create Ref
maine central
bangor and aroostook
boston and maine
grand trunk
vermont central
boston and albany
new haven
delaware and hudson
new york, susquehanna, and western
erie-lackawanna
chessie system
lehigh valley
long island railroad
penn central
#create oldrr
maine central
bangor and aroostook
boston and maine
grand trunk
vermont central
boston and albany
new haven
delaware and hudson
new york, susquehanna, and western
erie-lackawanna
chessie system
lehigh valley
long island railroad
new york central
pennsylvania
#user
#cmp newrr Ref
#log
#next
21.1a 10