<Table> <Tr> <Td> a </Td> </Tr> <Tr> <Td> </Td> </Tr> </Table> <Tr> <Td> a </Td> </Tr> <P> We also have a block for each position transition the machine can make, showing how the tape head moves, how the finite state changes, and what happens to the surrounding symbols . For example, here the tape head is over a 0 in state 4, and then writes a 1 and moves right, changing to state 7: </P> <Table> <Tr> <Td> q 0 </Td> </Tr> <Tr> <Td> 1q </Td> </Tr> </Table>

Show that the post correspondence problem is undecidable