COE428 Lab 4: State Machine

 

1. IMPORTANT: Two week lab

Note that you have two weeks to complete this lab. This lab must be submitted at least 48 hours before the beginning of your next lab period.

 

2. Prelab preparation

Before coming to the lab you should:

·         Read the lab. Try to prepare any questions you may have about the lab.

·         Refer to Lab Guide.

·         Create your lab directory for lab4. (i.e. use mkdir lab4 within your coe428 directory.)    

·         Change to your coe428/lab4 and unzip the lab4.zip file with the command: 

               unzip     /home/courses/coe428/lab4/lab4.zip
 

No errors should be reported.

Note

The command /home/courses/coe428/bin/getLab4 will execute properly only on a Sun Workstation. If you are using a computer other than a Sun workstation, please ssh to a Sun Workstation. (For example, ssh genesis.ee.ryerson.ca)

 

3. Requirements

The requirements to complete the lab are summarized below.

1.      Draw a diagram of your state machine.

2.      Create an executable program simState (based on C source code) that is able to respond to the commands described below.

3.      Your program will be presented with zero or more commands from stdin (each on a line by itself) and must respond precisely as specified for each command as listed below.

No Commands:

Before any commands are issued to your program, it should print out the starting state.

One/Zero Commands:

These commands (a `0' or a `1' on a line by itself) must print to stdout the name of the next state given the supplied input, and update the current state.

Change command:

The change command is invoked by the letter `c' followed by a `1' or a `0' followed by the name of a state (i.e. a single letter in the range A–H). This command modifies the state machine such that the `0' (or `1') command applied to the current state will cause the machine to change to the named state and that this change is the state machine configuration will continue. This command should produce no output.

Print command:

The print command is invoked with the single letter `p'. It should print to stdout the state machine configuration as currently specified (i.e. including changes that may have been made with change commands) in the same format that your state machine was specified with.

Garbage Identify command:

This command is invoked with the single letter `g'. It should identify all states that are reachable or unreachable from the current state. It always produces output to stdout.

If all states are reachable, it should output No garbage. Otherwise, it should output

Garbage: <unreachable states> where <unreachable states> is the list of the state names that are no longer reachable.

Delete command:

This command is invoked with `d', optionally followed by the name of a state to delete. When the ‘d’ command is invoked without the optional argument, it should delete (i.e. mark as “deleted”) all un-deleted states that are unreachable. If there are no such unreachable un-deleted states, it should print:

No states deleted.

Otherwise, it should print the message:

Deleted: <list of deleted states>

If the ‘d’ command is followed by an argument that it the valid name of a state, it should print out either the message:

Deleted.

if the state is not reachable and not already deleted. Otherwise, it should print out the message:

Not deleted.

If a state is successfully deleted, it should no longer appear in the list of states produced by the print command and it should be disallowed as a final argument to the change command.

4. Example

The description of a state machine is given in a text file where each line has the following format:

<StateName> <NextState0> <NextState1>

 

The <StateName> is the name of the state being defined, <NextState0> is the name of next state if the input is `0'; and <NextState1> is the name of next state if the input is `1'. All state names are single uppercase letters.

For example, given the state machine description and the information that the initial state is `C':

A B C

B A A

C A D

D D C

 We can draw a picture of the state machine as shown below.

 

Figure1

Figure 1 State Machine Diagram

Sample input and output is:

Interface

Comment: Input or Output

C

Output

0

Input

A

Output

0

Input

B

Output

c 0 C

Input

0

Input

C

Output

p

Input

A B C

B C A

C A D

D D C

Output

g

Input

No Garbage

Output

c 1 B

Input

g

Input

Garbage: D

Output

d

Input

Deleted: D

Output

p

Input

A B C

B C A

C A B

Output

 

Submit your lab

1. Go to your coe428 directory

2. Zip your lab4 directory by using the following command:

      zip   -r   lab4.zip   lab4/

3. Submit the lab4.zip file using the following command:

       submit   coe428   lab4   lab4.zip

 

 by Ken Clowes, revised by Ivan Lee, revised by Olivia Das