KEY. A 1. The action of a grammar when a derivation can be found for a sentence. Y 2. program written in a High Level Language

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1 1 KEY CS 441G Fall 2018 Exam 1 Matching: match the best term from the following list to its definition by writing the LETTER of the term in the blank to the left of the definition. (1 point each) A Accepts L Lexeme W Rejects B Assembly M Lexical X Scanner C Code Generator N Linear Bounded Y Source D Compiler O Machine Code Z String Table E Constrainer P Non-Deterministic AA Symbol Table F Deterministic Q Non-Terminals AB Target G Finite State R Optimization AC Terminal H Goal (or Start) S Parser AD Token I Grammar T Phrase/Structure AE Turing Machine J High Level Language U Productions K Interpreter V Push Down A 1. The action of a grammar when a derivation can be found for a sentence. Y 2. program written in a High Level Language AB 3. program translated into a Low Level Language, usually Assembly, Machine Code or Virtual Machine Code. K 4. software that translates statements of a source (usually) one statement at a time into Machine Code, then executes the translated statement before translating/executing the next. O 5. A Programming Language that has binary representation simple commands and differs by CPU model. Knowledge of the CPU/Hardware is required to program in this language. AE 6. An automata that has an infinite tape, can read/write/advance/rewind its tape, and uses an Unrestricted grammar. F 7. describes a grammar where, for any given situation, only one production may be chosen as a substitution. H 8. The Symbol is a special Non-Terminal that represents all possible valid sentences (programs) in a language. S 9. Major component of a compiler that takes a sequence of tokens and builds an Abstract Syntax Tree of the tokens, based on the rules of the language. N 10. An automata that has a finite tape, can read/write/advance/rewind its tape, and uses a Context Sensitive grammar. V 11. An automata that has a finite tape, can only read its tape, and only one time, and uses a Stack to implement a Context Free Grammar.

2 Z 12. The stores the exact spelling of identifiers and literals discovered by the scanner. 2 AA 13. The stores semantic information on tokens. L 14. A(n) is the string representation of a single word or symbol extracted from the source. AD 15. A(n) is a simplified (integer) representation of a Lexeme. It may be an object/structure containing members/fields describing a single word or symbol from the source. R 16. The process of making changes to the DAST and/or Target Code generated by a compiler to make the Target program more efficient. I 17. A(n) defines (formally) the correct forms of sentences (programs) of a language. U 18. are a set of rules where each rule specifies a string of terminals/non-terminals that can substitute for another set of terminals/non-terminals T 19. A(n) Grammar defines the correct formation of tokens into sentences (programs) for the language. Q 20. A(n) is a symbol that represent possible combinations of words/symbols/characters in a language; used in and defined by Productions. 21. Draw and label the Structure of a Compiler Diagram, including - The four major components (label with their name) [1 pt each = 4 pts] - The input/output files (label with their name) [1/2 pt each = 1 pt] - The two major data structures (tables) (label with their name) [1/2 pt each = 1 pt] - Arrows showing the flow of information (label with the information transferred) [0.2 each arrow = 2pt] [10 points]

3 3 22. Draw a diagram of the results of inserting items into a Hash Table similar to the one you wrote for Project 2. [8 points] - items consist of only digits - hash function: is simply the last (or only) digit in the item. hash(123)=3, hash(2)=2, hash(4567)=7 - the hash table is an array of 10 buckets, indexed each bucket is a linked list of nodes - collisions are attached at the end of the linked list. Insert in order: pt for array of pointers 1 pt each for each bubble in correct bucket and order 23. Complete the following table of the Chomsky Hierarchy, where Class 0 is the least restrictive classification. For the Production column, give an example of a grammar production for the class that would not satisfy the requirements of a higher class. Use lower-case letters for terminals and upper-case letters for non-terminals. (do not answer with an empty production, even though that would be correct in some cases). [8 points] Level Grammar 0.5 pt each Recognizer 0.5 pt each Production Example 1 each 0 Unrestricted Turing Machine abcxy d 1 Context Sensitive Linear Bounded Automata axb cdyzef 2 Context Free Push Down Automata X ayczd 3 Regular Finite State Automata X ay 24. List and describe the four elements of the formal definition of a General Grammar: [8 points] - set of terminals (alphabet) N set of non-terminals P set of productions S Goal Symbol S N 1 pt for each symbol (left of --), 1 pt for each description

4 25. Draw an FSA (graphical form) for block comments in C/C++ The rules are: [8 points] - must begin with /* and must end with */ - inside the comment, any character is allowed including * and / that are not consecutive in the order */ - use to represent all characters other than * and / - you may use empty productions if you wish - example: /*** /* //** this is a valid single comment ****/ 4 Answer: -1 if /* is one arrow. -3 if it works for /* ab */ but not the example shown above. / and may be on separate arrows 26. Given the following graphical FSA, write the formal/mathematical grammar of the language. You may use either the (N,t) = N or N tn format to write the productions. [10 points] = { a, b, c, e, f, g } (none off for d) [1.5 pt] Q = { S, X, Y, Z } [1.5 pt] = { (S,a) = S, (S,b) = X, (S,c) = Y (X,b) = X, (X,e) = Z, (Y,f) = Z, (Z,g) = Z } OR={ S as, S bx, S cy X bx, X ez, Z Y fz Z gz } [5 Pts 4 ] q0 = S F = { Z }

5 27. Using the productions in #26, draw a parse tree or write a derivation showing the sentence abbeg is accepted by the language. [6 points] 5 [about 1 pt per step or bubble; first error -0; -1 for others] OR: S as abx abbx abbez abbegz abbeg Start S as S bx X bx X ez Z gz Z 28. Given the FSA in #26, express the FSA in Table Form. Mark halt states with * [6 points] a b c e f g S S X Y X X Z Y Z Z* Z pts for each entry in the table, correct entry in correct position (7 total) - 1 pt for correct states in the first column - 1 pt for correct alphabet in the first row pt for star on Z 29. Using the FSA in #26, write a Regular Expression to define the language. Use only the formal metasymbols used in class do not use symbols from computing languages, etc. [6 points] a*((b + e) (cf))g* - starts with a* 1pt - ends with g* 1pt OR - contains (b*e) or (bb*e) 2pts - contains (cf) 1 pt a*((bb*e) (cf))g* - uses and parenthesis correctly 1 pt

6 6 30. Write the Algorithm for implementing an FSA. Assume productions and halt states are somehow identified. Use readchar() to represent reading the next character from the input file, and that it returns an EOF character at the end of file. [10 points] state = start c = readchar() while c!=eof and state!= error { state = get production based on state and c to get the next state if no production found state = error else c = readchar() } [2 pts] [1 pts] [0.5 pt] [0.5 pt] [0.25 pt] [0.5 pt] if c==eof and state is a halt state [2 pts] ACCEPT [0.5] else [0.25] REJECT [0.5]

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