2.5.4.8 REPLACE Command
  The REPLACE command writes a copy of the current pro-
  gram back to disk. It replaces it using the file specification
  specified in the last OLD command. Part or all of this file
  specification can be overwritten with the RENAME com-
  mand; whatever parts are not specifically changed remain
  the same. RENAME is similar to SAVE except that while
  SAVE copies the current program to the default directory,
  REPLACE copies the current program to the location speci-
  fied in the program's current file specification.

  After execution of a REPLACE command, BASIC issues an
  informational message confirming the file specification.