<Tr> <Th> Species </Th> <Td> Xylok </Td> </Tr> <Tr> <Th> Home era </Th> <Td> Early 21st century </Td> </Tr> <P> Mr Smith is a fictional extraterrestrial computer voiced by Alexander Armstrong which appears in the British children's science fiction television series, The Sarah Jane Adventures, with further minor appearances in the final two episodes of the fourth series of Doctor Who . He is installed in the attic of Sarah Jane Smith's home, and is used to hack into other systems; Sarah Jane asserts that he can hack "into anything". He first appeared in "Invasion of the Bane", the 2007 New Year's Day première special, and has appeared in all the stories except The Eternity Trap . </P> <P> Mr Smith is a Xylok, a member of a crystalline race which crashed to Earth as a meteorite some 60 million years in Earth's past . It was trapped underneath the surface of the Earth until the eruption of Krakatoa brought a single, small Xylok to the attention of geologists . Sarah Jane received the crystal from a geologist friend as an aid to her studies in volcanic activity . She found that the crystal could communicate with her laptop; it revealed to her that it could help her track alien life and protect the earth . To this end it is the core of the supercomputer known as Mr Smith . </P>

Who is mr smith in sarah jane adventures