27.8.13

The Six Turing Primitives

Alan Turing defined the six foundations of complete computability and manipulation of computer memory. Any computational device capable of these six functions can perform the work of any other device, no matter how complicated. That doesn't mean it can do it as quickly, but indeed, a Timex Sinclair, programmed to do so, can render the same computations as the XBox. Because at the root, they are both doing this:
Right:  move the machine head to the right

Left:  move the machine head to the left
Print:  place a symbol into the current cell
Scan:  identify any symbols in the current cell
Erase:  erase any symbols in the current cell
Halt: do nothing

28.5.13

Seasons of the Plague

Mild winters, cool moist springs, and early summers are reportedly the worst times for the Black Death.