16. A computer readable medium having computer-executable commands that, when executed, perform acts comprising: receiving a low level language instruction from a program block, the instruction include a word having a first type, the word being stored at a position in one of a stack or a heap of a memory, each of the stack or heap includes one or more specified positions and one or more unspecified positions; assigning a second type to the memory that includes the first type; and determining whether the low level language instruction is well-typed by applying one or more rules to the instruction and to the second type.
18. The computer-readable medium of claim 16 , further comprising a command that performs the act of applying an unpack rule to the instruction.