The only additional python module that is used is pygame, which can be installed with the command
python -m pip install -r requirements.txt
States can have any name, although short names (e.g. 0, S1, 3B...) are recommended as they appear nicely on the read-write head and in the transition function table during simulation.
Any string can be read from or written to the cells on the tape, although single characters are recommended as they appear nicely during simulation.
When defining an instruction, the direction refers to the movement of the head, and must be l or r (case-insensitive).
When defining an instruction, reading/writing a blank cell is represented by a blank entry.
Be careful of whitespace (accidental spaces) when defining your instructions - they can lead to unexpected errors.
The start position of the tape is the position at which the read-write head will be when simulation begins.
The blank character of the tape is what will be drawn at any blank cell on the tape. This can be left empty.
Each step of the machine consists of 4 parts:
- Read the current cell and find the corresponding transition instruction
- Write the new string
- Transition to the next state
- Move the read-write head
The read-write head will turn red if it is in a situation with no defined transition function.
The read-write head will turn green if it reaches an accept state.
The status of the machine is indicated by the symbol at the top-left of the window:
| Symbol | Meaning |
|---|---|
| … | Standby |
| ► | Running |
| ❚❚ | Paused |
| ■ | Stopped |
- SPACE: Do one full step
- T: Do one part of a step
- R: Run machine automatically
- P: Pause animation
- Esc: Interrupt machine (bringing it back to standby at the end of the current part of the current step)
- P: Unpause animation
- Left: Move head left
- Right: Move head right
- Up: Raise head
- Down: Lower head
(Manually raising/lowering the head has no practical purpose, only demonstrational purpose.)
- Tab: Toggle detail
- Equals: Zoom in
- Minus: Zoom out