Faces

Some devices work on a side of a block: a redstone card reads and sets the signal on a face, a robotic piston points one way. Every such device names a side the same way.

The names

A face is a string, only. There are two kinds of name.

The world’s names are Minecraft’s own: north, south, east, west, up and down.

Names relative to the block’s front are front, back, left and right. Left and right are as someone standing in front of the block, facing it, sees them (as a desktop case’s left side panel is on your left as you face it).

A program written with relative names works however the block is turned, and two programs written for the same block compose. A program written with the world’s names always means the same side of the world.

Devices always answer with the world’s names, so a program that reads a face back sees north, never front.

Which blocks have a front

Every block that holds devices has a front with its own look, facing the player who placed it: a case’s front, a hub’s card bays. A robotic piston’s front is opposite its cable port. The block tells its devices where it is.

A device with no block to say where its front is takes only the world’s names. Asking such a device for front fails with a message saying so. left and right also fail on a block whose front is up or down, because they would mean nothing.

Example

A redstone card in a case whose front faces north. In mcos, its /dev file takes a line a face (see /dev):

$ echo "front 15" > /dev/redstone0
$ cat /dev/redstone0
north 15 15
...

The first line puts a signal of 15 out of the case’s front. The card answers with the world’s name: that face is north. Each line is face level powered: the signal now on that face, and how much of it this card puts out. The other faces follow, one a line.