Automata and compiler, Theory of Computation

Automata and Compiler

(1) [25 marks] Let N be the last two digits of your student number. Design a finite automaton that accepts the language of strings that end with the last four bits of the binary expansion of N. (1.1) Make a regular expression ? of this language. For example the set of strings that end with 101 is expressed by a regular expression (0+1)*101. (1.2) Make an NFA that accepts this expression ?. You should remove any ?-moves that can be done trivially by inspection. (1.3) Make a subset automaton that accepts the language. (1.4) Perform state minimization on the above automaton.

(2) [25 marks] A CFG is given by S ? aSbS, S ? bSaS, S ? c

(2.1) Draw a syntax chart for this grammar. [5]

(2.2) Write a Python program for the recursive descent parser Trace the parser using two strings of at least 10 symbols, one for an accepted case and one for an unaccepted case. Do the trace using the style in the notes. [20]

(3) [25 marks] A sample program for computing the greatest common divisor by recursive call and its object program are given below. Some sample comments are given.

const a=75, b=55;

var x, y;

procedure gcd;

var w;


if y>0 then begin


y:=x ? (x/y)*y;


call gcd;




x:=a; y:=b;

call gcd;



0 jmp 0 21 Jump to 21, start of main

1 jmp 0 2

2 inc 0 4

3 lod 1 4

4 lit 0 0 Load literal 0

5 opr 0 12 Test if y>0

6 jpc 0 20 Jump to 20 if false

7 lod 1 4 Load y

8 sto 0 3 Store in w

9 lod 1 3

10 lod 1 3

11 lod 1 4

12 opr 0 5

13 lod 1 4

14 opr 0 4

15 opr 0 3

16 sto 1 4

17 lod 0 3

18 sto 1 3

19 cal 1 2

20 opr 0 0

21 inc 0 5

22 lit 0 75

23 sto 0 3

24 lit 0 55

25 sto 0 4

26 cal 0 2

27 lod 0 3

28 wrt 0 0 Write stack top

29 opr 0 0

Posted Date: 7/21/2012 11:19:01 AM | Location : United States

Related Discussions:- Automata and compiler, Assignment Help, Ask Question on Automata and compiler, Get Answer, Expert's Help, Automata and compiler Discussions

Write discussion on Automata and compiler
Your posts are moderated
Related Questions
The SL 2 languages are speci?ed with a set of 2-factors in Σ 2 (plus some factors in {?}Σ and some factors in Σ{?} distinguishing symbols that may occur at the beginning and en

Give the Myhill graph of your automaton. (You may use a single node to represent the entire set of symbols of the English alphabet, another to represent the entire set of decima

We will specify a computation of one of these automata by specifying the pair of the symbols that are in the window and the remainder of the string to the right of the window at ea

spam messages h= 98%, m= 90%, l= 80% non spam h=12%, m = 8%, l= 5% The organization estimates that 75% of all messages it receives are spam messages. If the cost of not blocking a

Theorem The class of ?nite languages is a proper subclass of SL. Note that the class of ?nite languages is closed under union and concatenation but SL is not closed under either. N

Computation of a DFA or NFA without ε-transitions An ID (q 1 ,w 1 ) computes (qn,wn) in A = (Q,Σ, T, q 0 , F) (in zero or more steps) if there is a sequence of IDs (q 1

Our primary concern is to obtain a clear characterization of which languages are recognizable by strictly local automata and which aren't. The view of SL2 automata as generators le

We now add an additional degree of non-determinism and allow transitions that can be taken independent of the input-ε-transitions. Here whenever the automaton is in state 1