Using the Interface

The applet interface is divided into two major parts: the machine display and the programming controls. The display includes the tape itself (with the current cell hilited in the center), arrows for scrolling it manually, and some controls used in running the program. "Start" resets the machine and runs it, "Stop" causes it to halt, "Resume" restarts the machine without resetting anything, and "Step" is used to execute a single transition. The "Speed" option may be set to "slow", "fast", "very fast", or "compute"--the last runs as quickly as possible and without displaying any of its operations on the tape, which is helpful mainly for testing Busy Beaver machines that may execute millions of transitions before halting. Upon halting the message box (in the lower right-hand corner of the applet) displays the reason for the halt, the total number of transitions in the run and the total number of non-blanks now on the tape, the last two of which are again mainly useful for Busy Beaver programs.

In the middle of the applet is a pull-down list with some preset Turing Machine programs that you can load and run. This is the easy way to do things; the programs are automatically installed upon loading. Choose the "<New>" option to reset all fields and to clear the programming box (see below).

Following this are some basic specs for the current machine: name (optional), initial position, and initial characters (optional--the tape may be blank to begin with), all of which may be set (initial position and initial chars can be changed without having to reprogram).

On the lower left is a text box for displaying and/or entering the transition table code for the current machine (see How to Program). This code is not actually set up to run until you press the "install program" button on the right. The other box on the right is just a catch-all message area to reflect what's going on in the rest of the applet.

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