Formal Languages

Question 1

Why do we have formal languages?

Answer 1

We need to communicate with machines. Natural languages are ambiguous and require the understanding of context

Question 2

What are the three keywords used to describe a language

Answer 2

Alphabet, syntax and semantics

Question 3

What is on alphabet

Answer 3

It is a non empty finite set of elements that make up a language

Question 4

How are words formed for a language

Answer 4

By concatenating one or more elements from an alphabet

Question 5

What is syntax in a language

Answer 5

Syntax is the form and structure of the language

Question 6

What are the 2 types of syntax that describe the structure of a programming language

Answer 6

Lexical. Syntax and phrase structured syntax

Question 7

What is lexical syntax

Answer 7

It is a type of syntax which describes the structure of a programming language.it defines how individual components come together to form meaning full tokens.it helps a computer understand which words, numbers or symbols are important and which are not, by defining keywords, operators and identifiers.

Question 8

How ave lexical syntax defined

Answer 8

They ave defined using regular expressions and other formal grammars

Question 9

What are phrase structured syntax

Answer 9

They describe the structure of a programming language. They define hour tokens come together to form larger structures such as expressions, functions and statements.it helps a computer understat how the may components fit together to create meaning. Eg: order of arithmetic operations, structure of control statements such if/else, syntax for function declaration and calls.

Question 10

How are phrase structured syntax defined

Answer 10

They are defined using context free grammars and other formal languages,

Question 11

What are semantics

Answer 11

Linguistic meaning of syntactically correct sentences

Question 12

What is an abstract syntax

Answer 12

Defines the logical stricture of a program i.e. Algorithms. Not dependendant ona programming
Language

Question 13

What is concrete syntax

Answer 13

Concrete syntax refers to the specific language or syntax used to express the abstract syntax of a program.

Question 14

What is a string

Answer 14

It is a word. Made by concatenating one or more elements from an alphabet. It is a finite sequence of symbols from an alphabet.

Question 15

How are elements from an alphabet and words denoted.

Answer 15

Lower case beginning letters are used to denote elements of an alphabet while lower case end characters are used to denote strings

Question 16

How can two stings v and W be concatenated

Answer 16

By appending w to the end of v

Question 17

What is a reverse of a string

Answer 17

It is the string written in reverse order

Question 18

What is lwl

Answer 18

It is the length of a string w.

Question 19

What is €

Answer 19

It is a empty string of length zero it is I€l=0

Question 20

If w=uv then what are u and V

Answer 20

U is the prefix of W and vis the suffix

Question 21

If w=abbcab, then what are the set of prefixes

Answer 21

{ A, ab, abb, Abbc, abbca, abbcab }

Question 22

If W is a string, then what is w to the power n

Answer 22

W to the power n is the string obtained when w is concatenated by itself n times

Question 23

It £ is an alphabet then what is £ to the power k

Answer 23

It is the string of length K that can be obtained from that alphabet

Question 24

What is kleene closure of an alphabet £ ( £ to the power *)

Answer 24

It is the set of all possible string from an alphabet