TOC UNIT 2B

Which of the following is a regular language?

• {aⁿbⁿ | n ≥ 0}

• {aⁿ | n is prime}

• {aⁿbᵐ | n, m ≥ 0}

• {aⁿbⁿcⁿ | n ≥ 0}

What does the symbol * (Kleene star) represent in regular expressions?

• Zero or more occurrences

• One or more occurrences

• Optional character

• End of input

Which machine accepts regular languages?

• Turing Machine

• Pushdown Automaton

• Finite Automaton

• Stack Machine

Which of the following is a valid regular expression?

• a+b

• a(b|c)*

• (a|b)*abb

• All of the above

What does (a|b) mean?

• Strings with exactly one a or b

• Strings of only a's

• Any string made of a's and b's

• Only empty string

Is the empty set a regular language?

• Yes

• No

• Sometimes

• Only for DFAs

What is the language of the regular expression a?

• Only strings with one a

• Strings with no a

• Strings with zero or more a's

• Strings with only b's

What is the use of a DFA in regular languages?

• Proves language is not regular

• Generates strings

• Accepts or rejects strings

• Replaces regular expressions

Which of the following is true for regular languages?

• Closed under union

• Closed under concatenation

• Closed under star

• All of the above

Regular expressions can describe:

• Context-free languages

• Only finite strings

• Regular languages

• Infinite languages only