3. Input Tape
The Part of FA where the input lives is called Input Tape
The Location is which we put input letter is called cells
4. Example Of Input Tape
The Example of tape that contain some of our input letter
Here ∆ is used to indicate the blank in the tape cell
Means that this cell is empty and we can place a letter into this cell
5. Input Tape:
Properties
As we process the tape onto the machine
We read one letter a time
After reading the letter we will eliminate that letter assuming that it is
used
When we will read first blank cell we will stop because we will assume
that after first blank cell all other cells will also be blank
And we read cells from Left To Right
6. Start / Reject / Accept
A start State is a state from where we begin the process but read inputs no
letter
Start
A start state has no arrow coming into it
A reject state Is dead-end non final state, where all the input is consumed
but we did not achieve the goal
Reject
A Accept state is a dead-end a final state tells that the input is accepted
and we have achieved our goal
Accept
7. Read State
We are changing our diagrams so an important thing in our FA’s was to
read a letter and then decide where to go so in pictorial representation
we have introduced a READ state.
Read state is just like a diamond shape.
8. Remember
When the character ∆ is read from input tape means that we are out of
input
Then we Finish Processing
The ∆-edge will lead us to accept state if the state have stop into final
Other wise it will lead us to reject state
In old methods we have no idea when we are out of inputs
10. What is the benefit????
It just like flow chart so what is the reason to use this and
Using Pictorial representation we still representation the FA’s so how can
we give more power to our machine?????
For this purpose we will use the “STACK”
It is easy to use stack with these pictorial representation
11. Stack:
Push Down Stack/ Push Down Store
A stack is a storage point where we can store our input letter
And then call them back when we will refer it
Stack Pointer: That point the top of the stack
It has two main Operations
Push
POP
12. PDA:
Push Down Automata
When FA’s have been souped up with the
Stack
Push
Pop
Then we call it the push down automata abbreviated as PDA’s
By adding this data structure the language recognizing capability is increased.
13. How To Define a PDA
A push down automata is collection of 8 things
An alphabet ∑ (Segma)of input letters
An input Tape
An Alphabet (Taa) of stack character
A pushdown stack
On start State
Halt States
Push State
Read State
State Read Top of stack
