When the initialization TECO macro is executed, the following
  conditions are in effect.

   Text buffer   User's editing command
   Q-register 0  Initialization TECO macro itself
   Q-register 9  TECO's built-in command decoder data storage
   Q-register Y  TECO's built-in command decoder TECO macro

  The user's editing command in the text buffer can be modified
  by the initialization TECO macro.

  All other Q-registers are initially scratch and can be used or
  loaded by the initialization TECO macro; their contents will
  subsequently be preserved.