Undo Options
The availability of the "Undo" command depends on the following options:
Specify how many sequential actions are to be reversed by the Undo command. This option does not affect the number of reversible keyboard inputs, which is only limited by the available RAM.
In order to save time and space on your hard disk, you can specify a file size limit. If a file is larger than this limit, backups will not be created and the Undo command is not available except for keyboard input.
Automatically created backups for the internal use with the Undo command are deleted by WinHex when closing the file, if the corresponding option is fully selected If it is partially selected, they are deleted when WinHex terminates.
Choose for all kinds of editing actions whether they should be reversible or not. In case they should, an internal backup is created before the action takes place.