I've heard that computers cannot forget anything, but yesterday my teacher told me that a computer can lose its memory from getting very hot. Is that true that computers can lose information? How and why does this happen? Can the lost information be retrieved back?
Beside the physical destruction of hardware, raising temperature has negative impact on computer storage :
- Magnetic material loose magnetisation faster
- Leakage current in DRAM, FLASH. FLASH SSD content will last longer if it is stored in cool environment. DRAM memory, when not properly refreshed, will loose its contents faster.
- Current in static RAM is higher with higher temperature, if memory is battery backed, the battery with keep the charge for a shorter time.
All these components are therefore designed with specific usage conditions, and as long they are respected, data should not be lost.
It depends on what "memory" you are talking about. Basically, nothing in a computer can contain data forever. Random Access Memory in a computer loses its data after it is no longer powered, a hard drive has a data retention of approximatively 10 years (this may be different now because of SSDs/SSHD/etc, but you get the idea). There are also several cases where a memory becomes amnesic, but knowing that there are many types of technology for memory, it can vary greatly. It is sometimes possible de retrieve lost data, but again, it depends on the technology.
Heat your computer up to 2,000 degrees Celsius, and all that is left is a large puddle of molten material, plus some rather noxious gases. All memory will be gone. Actually, most memory will be erased at much lower temperatures.
To erase the memory on a hard drive completely, an angle grinder would probably do a good job. (You'd need very strong magnets).
But obviously a computer can forget everything if you just tell it to forget it. Everything on your hard drive can be erased, all RAM can be erased, and then things are forgotten.
Another method works when data is stored in an encrypted form: All you need to do is erase the decryption keys. The data is still there, but absolutely inaccessible.