Second World WAR and ENIGMA MACHINE's working Method

An Enigma machine is made up of several parts including a keyboard, a lamp board, rotors, and internal electronic circuitry. Some machines, such as the ones used by the military, have additional features such as a plug board.
Encoded messages would be a particular scramble of letters on a given day that would would translate to a comprehensible sentence when unscrambled.

When a key on the keyboard is pressed, one or more rotors move to form a new rotor configuration which will encode one letter as another. Current flows through the machine and lights up one display lamp on the lamp board, which shows the output letter. So if the "K" key is pressed, and the Enigma machine encodes that letter as a "P," the "P" would light up on the lamp board.

Each month, Enigma operators received code books which specified which settings the machine would use each day. Every morning the code would change.

For example, one one day, the code book may list the settings described in the day-key below:

1.Plug board settings: A/L – P/R – T/D – B/W – K/F – O/Y

A plug board is similar to an old-fashioned telephone switch board that has ten wires, each wire having two ends that can be plugged into a slot. Each plug wire can connect two letters to be a pair (by plugging one end of the wire to one letter’s slot and the other end to another letter). The two letters in a pair will swap over, so if “A” is connected to “Z,” “A” becomes “Z” and “Z” becomes “A.” This provides an extra level of scrambling for the military.

To implement this day-key first you would have to swap the letters A and L by connecting them on the plug board, swap P and R by connecting them on the plug board, and then the same with the other letter pairs listed above. Essentially, a one end of a cable would be plugged into the "A" slot and the other end would be plugged into the L slot. Before any further scrambling happens by the rotors, this adds a first layer of scrambling where the letters connected by the cable are encoded as each other. For example, if I were to encode the message APPLE after connecting only the "A" to the "L", this would be encoded as LPPAE.

The plug board is positioned at the front of an Enigma machine, below the keys.
The plug board is positioned at the front of an Enigma machine, below the keys.

2. Rotor (or scrambler) arrangement: 2 — 3 —1

The Enigma machines came with several different rotors, each rotor providing a different encoding scheme. In order to encode a message, the Enigma machines took three rotors at a time, one in each of three slots. Each different combination of rotors would produce a different encoding scheme. Note: most military Enigma machines had three rotor slots though some had more.

To accomplish the configuration above, place rotor #2 in the 1st slot of the enigma, rotor #3 in the 2nd slot, and rotor #1 in the 3rd slot.

3. Rotor orientations: D – K –P

On each rotor, there is an alphabet along the rim, so the operator can set in a particular orientation. For this example, the operator would turn the rotor in slot 1 so that D is displayed, rotate the second slot so that K is displayed, and rotate the third slot so that P is displayed.