text: Q:
  
  `0a1` in the output of diff file1 and file2
  
  Upon comparing two files and get the result:
   diff alpha_rsa.pub authorized_keys
  0a1
  > ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDBj3chjFnpxtHfeSUJVFv6fIN4CPZmIlBzuhMOOJNpovQqBc5JAhrz9uRiQIMHPD2vW+QJYiK08+6pCHthQSFrSLokLXTJfqEvb+frNEc6HvPPglGY3//97lbxR+CQYTjB/XgvnrP8sWKRt4VLfCwtCE6TqdVMx1y9SUmf7FghbHWhUioezdJaFJmfR+WVtELrUSwsc5eXcF+RS74eXEys2/v7LJF2JNYZxu0+Et7EwgxliA/5bOo6jTKBSZttBZPlsn2N7/GXnDilfAy06Iuc8MzMFCrAajQx8Nd4DG5Y33YyNVfU7eat9btUqNhpKGC+b5FGY4mkIPA2tammnjkx
  
  I am aware that the output is the difference. 
  What does 0a1 mean? which cannot be found from the manual.
  
  A:
  
  After line 0 (i.e., beginning) of the first file, a dd the following line (1 st line from the second file).
  Note: Since these are ed commands, you should look at the ed man page: http://manpages.ubuntu.com/manpages/disco/en/man1/ed.1plan9.html
  Also, google diff command tutorial for more examples.
  
  