With the dealer's scan tool.
Disconnect the battery for at least several minutes. That should clear all codes in memory
Go right all the way to the purple tab and click memory and you can clear your memory device
Most (if not all) key fobs can be recoded. You may want to inquire with your dealership or a good locksmith.
To clear a Dreamcast memory pack connect it to a Dreamcast via a controller. Start the Dreamcast without a disc in the drive and wait for the main menu. From the main menu select "File" and then select the memory card you wish to erase. Press left to highlight the "all" option and press A. From the menu select "delete (memory reset)". The Dreamcast should then clear the memory of all data.
One is clear, the other is clear everything. Use clear to just change the last number you put in. Clear everything to start all over again. The other keys relate to memory, of which your calculator seems to be able to store *one* number. MC clears the memory (sets it to zero).. MR recalls the memory (puts the number from memory into the display, so that you can add to it or whatever. MS stores the number on the display into memory. M+ adds the nmuber on the display to the number in memory
Bring all keys and FOBs to dealership.
Generally All Clear, though it is usually CA for Clear All. This clears the display and all internal registers except possibly (M+, MR) memory, which is cleared separately with the CM key.
When you turn it off, all memory is lost. You usually end up with pseudo-random patters. To actively clear all mem would require a machine language program ... which would be wiped in the process.
Remove the Positive (red) battery cable from the battery for 1 minute. This should clear all memory presets (radio, seat, stored computer error codes, etc).
Press 2ND MEM (above +). Then select option 7, "Reset...". Select All RAM and press yes. This clear clear all memory except for your applications (such as your games).If you want to clear absolutely everything, then instead if choosing All RAM, go over to ALL and choose All Memory... and press yes. This will delete EVERYTHING, so make sure this is what you want.
As far as I know only the dealer can do this for you. When you bring the car to the dealer have all keys and keyless entry fobs with you as they all have to be recoded.
Press second (2ND) and then memory (MEM, above +). Then select the seventh option, Reset.... In order to delete everything, use the arrow keys to select ALL on the top and then press enter to select All Memory....