#print
Now that you know how to add lines to a file,
you will want to know how to get rid of them.
The command
   5d
will delete line 5 of a file.  The command
   .d
will delete the current line.
In the file 'pres' either the 5th or 6th line
is wrong.  Print those lines and delete the bad
one; then rewrite the corrected file.
Then type 'ready'.
#create Ref
george washington
john adams
thomas jefferson
james madison
james monroe
john quincy adams
andrew jackson
martin van buren
william henry harrison
john tyler
#create pres
george washington
john adams
thomas jefferson
james madison
james monroe
 this is wrong Qwertyuiop
john quincy adams
andrew jackson
martin van buren
william henry harrison
john tyler
#pipe
#user
#unpipe
#cmp pres Ref
#log
#next
19.1b 10