Toshiba C55-C User Manual page 30

Data save in Hibernation Mode
When you turn off the power in Hibernation Mode, the computer takes a
moment to save the current data in memory to the Hard Disk Drive.
After you turn off the computer, and the content of memory has been saved
to the Hard Disk Drive, turn off the power to any peripheral devices.
Do not turn the computer or devices back on immediately. Wait a moment
to let all capacitors fully discharge.
User's Manual 2-13