An error occurence in a computer's memory system that changes an instruction in a program or a data value. Soft errors typically can be remedied by cold booting the computer. A soft error will not damage a system's hardware; the only damage is to the data that is being processed.
There are two types of soft errors:
chip-level soft error: These errors occur when the radioactive atoms in the chip's material decay and release alpha particles into the chip. Because an alpha particle contains a positive charge and kinetic energy, the particle can hit a memory cell and cause the cell to change state to a different value. The atomic reaction is so tiny that it does not damage the actual structure of the chip. Chip-level errors are rare because modern memory is so stable that it would take a typical computer with a large memory capacity at least 10 years before the radioactive elements of the chip's materials begin to decay.
system-level soft error: These errors occur when the data being processed is hit with a noise phenomenon, typically when the data is on a data bus. The computer tries to interpret the noise as a data bit, which can cause errors in addressing or processing programcode. The bad data bit can even be saved in memory and cause problems at a later time.