ed by Ken Thompson

Edit lines with ed.

Commands
a  append
c  change
d  delete
e  edit
f  file
g  global
i  insert
j  join
k  mark
l  list
m  move
n  enumerate
p  print
P  prompt
q  quit
r  read
s  substitute
t  transfer
u  undo
v  exclude
w  write
W  writeEOF
wq write;quit
!  sh
// search
?? rsearch

a append

W write to end of file
`a,`b W F   append `a,`b to F
W F         append buffer to F

Move Lines Between Files
`a,`b w temp
e file
`c r temp

Sources
http://pubs.opengroup.org/onlinepubs/009604599/utilities/ed.html
http://www.gnu.org/software/ed/
http://www.cs.princeton.edu/courses/archive/spr08/cos333/ed.c

Why ed? A sorcerer's spells are cast with ed.