PAPER

Department of Computer Science

University of Karachi

BSCS- Compiler Construction

Q1) Select true or false of the following.

1. All variables must be declared before they are used. True / False

2. The expressions a + b % c and (a + b) % c are equivalent. True / False

3. The expressions a - b - c and a - (b - c) are equivalent. True / False

4. The expressions 15 / 3 and 15 / 3.0 are equivalent. True / False

5. The following declaration is used to declare a variable with Boolean type.
bool flag ; True / False

6. If str is a string variable that holds the string "The good life", then str[3] refers to the character 'e'. True / False

7. A header file typically contains type definitions, function prototypes and the implementations of the function. True / False

8. If a function has a local variable x and there is also a global variable called x, then the statements in the function which use x refer to the local variable. True / FalseA lexical analyzer transforms a stream of tokens into an AST (Abstract Syntax Tree). True / False

9. Lexical analyzers based on a FSA (Finite State Automaton) efficiently match multiple token descriptions concurrently to the input stream. True / False

10. Each input character is inspected only once. True / False

11. A lexical analyzer generated by lex is essentially a FSA. True / False

12. A parser transforms a stream of tokens into an AST (Abstract Syntax Tree). True / False

13. A lexical analyzer generator automatically constructs a FSA (Finite State Automaton) that recognizes tokens. True / False

14. The generator is driven by a regular description True / False

15. A parser transforms a stream of characters into a stream of tokens. True / False

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Q2) Select one from the following- MCQs

1. In C, the term ``white space'' means:
a. A single space, tab or new-line character.
b. Several spaces, tabs or new-line characters.
c. Any combination of spaces, tabs and new-line characters.
d. All of the above.

Your answer: ______

2. What is the value of the integer expression: 1 - 3 * 5 + 6 / 4 % 2
a. 0
b. -6
c. -8
d. -13

Your answer: ______

3. By the rules of short-circuit evaluation, in the following expression,
p || ( n < style="">
a. if p is true, then n <> will not be evaluated.
b. if p is false, then n <> will not be evaluated.
c. if p is true, then n <> will be evaluated.
d. None of the above.

Your answer: ______

4. If p and q are Boolean variables, which expression is equivalent to the following expression?
! ( p || q)
a. !p || !q
b. p || q
c. !p && !q
d. p && q

Your answer: ______

Q3) Give unambiguous grammar of Algebraic expressions that parse +, -, *, / and ^ operators as well as ++ increment and -- decremetn operator.

Q4) Give selection set of the grammar of Q1.

Q5) Give grammar that parse the following patterns.

a) 1ⁿ 0ⁿ

b) 1ⁿ0^m1^m0ⁿ

Q6) Give attributed translation grammar that parse if / else construct and generate appropriate jump, conditional jump and label intermediate instructions.