CS402 Midterm Subjective by VU Topper RM

Very Important Topics with Question. · 1) · What is FA.

Sol: In theory of automata, FA is a Finite Automaton, a simple machine that recognizes patterns in a sequence of symbols. It has a limited number of states and transitions based on input symbols. It accepts the input if it ends in a designated "final" state.

2)

What is NFA.

Sol: In theory of automata, NFA stands for Non-Deterministic Finite Automaton. It's a type of FA where: It can have multiple possible transitions from a single state for the same input symbol. (Think: choosing a path) It can sometimes move between states without any input (using epsilon transitions). (Think: taking a shortcut) This makes NFAs more flexible for representing certain patterns than regular FAs.

3)

What is GTG.

Sol: In theory of automata, GTG stands for Generalized Transition Graph. It's a way to represent a machine that's more powerful than a Finite Automaton (FA).

4)

Kleene star closure.

Sol: In theory of automata, the Kleene star (Σ*), applied to an alphabet (Σ), represents all possible strings of any length over that alphabet, including the empty string (λ). It basically means "zero or more repetitions" of symbols in the alphabet.

5)

Convert NFA into FA.

Sol: NFAs can be converted to Deterministic Finite Automata (DFAs). This process involves finding the epsilon-closure (all reachable states with epsilon moves) for each state in the NFA and building the DFA based on those closures. While NFAs can be simpler to design, DFAs are generally more efficient for simulation.

6)

What is the transition table.

Sol: A transition table is a table in automata theory that shows what state a machine (like a finite-state automaton) will move to based on its current state and the input it receives. Rows represent current states, columns represent input symbols, and entries show the next state. It's a compact way to represent the behavior of the automaton.

7)

Convert given TG into FA.

Sol: Unfortunately, I can't directly convert a Transition Graph (TG) into a Finite Automaton (FA) description (like a transition table) without the actual TG. However, I can give you a short answer on the conversion process: Identify States: Each node in the TG represents a state in the FA. Identify Start and Accepting States: Mark the designated start and accepting states in the TG as the same in the FA. Analyze Transitions: For each transition arrow in the TG labeled with an input symbol (a from the alphabet), create a corresponding entry in the FA's transition table. The row represents the source state (from the arrow's tail), the column represents the input symbol, and the entry shows the destination state (at the arrow's head).

8)

What is a regular expression.

Sol: In theory of automata, a regular expression is a concise way to describe a set of strings (a language) recognized by a finite automaton (FA). It uses symbols and operators to define patterns that strings must follow to be considered part of the language. Regular expressions are powerful for representing simple patterns like: Specific characters (a, b, etc.) Any character in the alphabet (.) Repetition (a*, meaning zero or more "a"s) Choice (a|b, meaning either "a" or "b")

9)

Length and reverse of string.

Sol: Finite Automata (FA) are not powerful enough to directly determine the length or reverse a string. They are limited to recognizing patterns within a string based on state transitions. Length: FAs can't count the number of symbols processed during transitions. They only accept or reject based on the final state reached after reading the entire string. Reverse: FAs operate by reading the input symbol by symbol, and their transitions depend on the current state and the current symbol. They don't inherently can process the string in reverse order.

10) String was given to make CFG.

Sol: Absolutely! We can attempt to create a Context-Free Grammar (CFG) from a given string. Here's a basic approach: