Turtles are essentially robots, and were added in the 1.3 update. They run an OS, like the Computers, named TurtleOS. They have the ability to place, break and detect blocks, move around and drop items in their inventory. The programs they run are stored on its internal memory or floppy disks.
The 1.4 update was focused on turtles, and expanded the turtle's ability to use tools. Turtles are capable of using pickaxes, hoes, axes, shovels and swords. The update added "Crafty Turtles", which have the ability to craft using their inventory - and part of this upgrade saw the number of inventory slots in the Turtle raised to 16 - over the previous 9 slot inventory. The 1.4 update also included a new fuel system for the turtles.
Turtles are submersible and lavaproof. As such, they are extremely useful for mining near bedrock, where heavy lava flows can prevent access to diamonds and other rare finds.
If you would like to know more about how to program them, have a look at the Turtle API.
Keep in mind, that turtles will not keep their programs unless they are labelled. To do so, you simply need to type in "label set labelName". This will label your turtle with the specified label, in this case "labelName".
Turtles use a Fake Player when moving and placing block in the world, as well as attacking entities. Each Turtle has a fake player named [ComputerCraft:<id>], where ID is the ID of the Turtle (obtainable by typing id into the Turtle). Turtles work and follow the permissions of all world protection and zone plugins if permissions are set for these fake players. All Turtles can be restricted by using the fake player [ComputerCraft]. Every turtle will attempt to identify as this fake player as well as [ComputerCraft:<id>].
Floppy Disks and Peripherals
Turtles do not have a built-in Disk Drive. As such, they need a Disk Drive placed beside them to access Floppy Disks. However, if the Turtle is of the Wireless family, the Disk Drive (and other peripherals) must be placed on a side other than the side the wireless modem is on. Any other peripherals, such as Monitors and Printers can be interacted using the peripheral API.
Turtles require fuel to operate - this means Turtles must be powered from any item that works in a regular furnace, like coal and lava. The turtle gains 0.6 "movement" per half second the fuel would have burnt in a furnace. The Turtle can move 1 block for each fuel count it has, for example, coal yields 96 block movements. For more information, go to the Turtle.refuel page.
Optional Non-fuel mode
In this mode, Turtles use their internal Redstone Engine, and as such, they do not need to be re-charged, or receive any other form of external power. This is because Redstone continuously emits low levels of energy, and the Turtle's engine is very efficient. This mode can be turned on by editing the turtle config file (config/mod_CCTurtle.cfg) and setting turtleNeedsFuel to 0.
Turtles equipped with a diamond hoe can till dirt so it can later be used for Farming. An example of a use for this would be using it to till, plant, and harvest your wheat farm and dropping any product in a chest for you.
Turtles crafted with a diamond pickaxe, diamond axe, or diamond shovel, can break blocks, chop wood, mine stone and ores, and even break dirt and gravel (depending on the tool you used on it). The tools equipped on the Turtle have no durability, and so can be used indefinitely without the need for any additional materials. When a Turtle breaks the block, the Turtle receives the item directly into it's inventory. Different tools yield different drops - for example, an axe can break anything, but it won't drop ores.
Turtles with a Crafting Table can craft items if they have the correct materials to do so, and all other slots outside the crafting-zone are empty.
Turtles equipped with a diamond sword can attack players and mobs. When a Turtle kills a mob it will leave the experience orbs on the ground, but add the loot to its inventory. Turtles can also attack with any tool, where the diamond axe is the second best after the diamond sword.
Turtles can interact with blocks that have inventories. This includes chests, furnaces, printers and even blocks with inventories in other mods. (This means a turtle cannot interact with a player's inventory). Turtles can interact with such inventories by using turtle.suck, turtle.suckDown, turtle.suckUp (To retrieve the first item in the inventory. The turtle finds the first item by scanning the first row from left to right, then the second row from left to right, ect.) Turtles can also place items inside inventories, by using turtle.drop, turtle.dropUp, turtle.dropDown, which places items on the first item slot available (Using the same system as the one described for retrieving items).
In special inventories, with just a few slots on the top or bottom, for example furnaces, you can specify which slot to place an item in by positioning the turtle in the corresponding location to the front face of the inventory. For example in a furnace, you would use a turtle at the bottom of the furnace for it to place fuel in the furnace, a turtle at the top to place objects to smelt, and a turtle to the right to retrieve the smelted objects (Note that you can do this with just 1 turtle moving around)
Turtles can be equipped with different peripherals and tools. A turtle can only have one tool and one peripheral, however the crafting table can act as a tool, or peripheral.
The following tools can be equipped to a turtles: diamond pickaxe, diamond axe, diamond shovel, diamond hoe and diamond sword
The following peripherals can be equipped to a turtles: wireless modem and crafting tables.
Diamond tools must be unused (i.e. not have a durability bar showing) to combine with a turtle.
Turtle recipe and examples for equipping a turtle with tools and peripherals.