Programming Languages Test 2 Revision 1 CMSC 4023 CRN Spring 2007

Transcription

1 1. Pr your name on your scantron in the space labeled NAME. 2. Pr CS 4023 in the space labeled SUBJECT. 3. Pr , the date in the space labeled DATE. 4. Pr your 24290, your CRN-number in the space labeled PERIOD. 5. You may not consult your neighbors, colleagues, or fellow students to answer the questions on this test. 6. Mark all selections that satisfy the question. If selection b, c, and d satisfy a question then mark selections b, c, and d. 7. Darken your selections completely. Make a heavy black mark that completely fills your selection. 8. Answer all 50 questions. 9. Record your answers on SCANTRON form 882-E (It is green!) 10. Submit your answers on Monday, April 2, 2007 at 7:30 a.m. in Room MCS 115 1

2 1. Select the correct binding time for the maximum number of significant digits in a real number. a. Language definition time b. Language implementation time c. Translation time d. Execution time 2. Select the correct binding time for the location of a local variable. a. Language definition time b. Language implementation time c. Translation time d. Execution time 3. Select the correct binding time for the meaning of a native type. a. Language definition time b. Language implementation time c. Translation time d. Execution time #include <iostream> using namespace std; a,b; void pr(void){cout << "a=" << a << " b=" << b;} p(& a){ p=2;a=0;b=1;return p;} void q(void){ b=4;a=3;pr();} main(){a=p(a);q();return 0;} Figure 4. C++ Program for Questions 4 and What is pred by the program in figure 4 assuming the symbol table employs static scope? a. a=1 b=3 b. a=2 b=4 c. a=3 b=1 d. a=3 b=4 5. What is pred by the program in figure 4 assuming the symbol table employs dynamic scope? a. a=1 b=3 b. a=2 b=4 c. a=3 b=1 d. a=3 b=4 2

3 program q06; var i,j,k:eger; procedure pr; begin{pr} write(' i=,i:2); write(' j=',j:2); write(' k=',k:2); writeln end{pr}; procedure p; var j:eger; procedure q; var k:eger; begin{q} k:=3; pr; end{q}; begin{p} j:=2; q end{p}; procedure r(var j:eger); begin{r} i:=-i; j=-j; end{r}; begin{q06} i:=-1;j:=-2;k:=-3; r(j); p; end{q06}. Figure 6. Pascal program for question What is pred by the program in figure 6 assuming the symbol table employs static scope? a. i=-1 j= 2 k=-3 b. i=-1 j=-2 k=-3 c. i= 1 j= 2 k=-3 d. i= 1 j= 2 k= 3 7. What is pred by the program in figure 6 assuming the symbol table employs dynamic scope? a. i=-1 j= 2 k=-3 b. i=-1 j=-2 k=-3 c. i= 1 j= 2 k= 3 d. i= 1 j= 2 k=-3 3

4 Variable Symbol Descriptor TypeKind ptype pid VariableS Color Offset 128 Enumerated Type Descriptor TypeKind pclist ptype EnumT Clist Type Descriptor TypeKind Size L Count CListT 2 3 Constant Type Descriptor TypeKind pid Value ptype ConstantT red 0 Constant Type Descriptor TypeKind pid Value ptype ConstantT green 1 Constant Type Descriptor TypeKind pid Value ptype ConstantT blue 2 Type Descriptor TypeKind TypeLength Alignment CardinalT Figure 8. Diagram for question Select the declaration(s) that match the representation shown in figure 8? a. type Color=(red,green,blue); {Pascal} b. var Color:(red,green,blue); {Pascal} c. enum Color {red,green,blue}; {C++} d. enum {red,green,blue} Color; {C++} 4

5 1. #include <iostream> 2. using namespace std; 3. a; 4. b; 5. p(& a) 6. { p=2; 7. a=0; 8. b=1; 9. return p; 10. } 11. void q(void) 12. { b=4; 13. a=3; 14. } 15. main() 16. { a=p(a); 17. q(); 18. return 0; 19. } Figure 9. C++ Program for question Assuming that compilation proceeds from line 1 to line 19 in figure 9, select the diagram(s) below that represent the symbol table at line 7. a & local to p() global a local to p() global b global b global p local to p() function global p local to p() function global diagram a Diagrams 9a and 9b. diagram b 5

6 a & a b b p function symtab p function symtab a a & p p diagram c diagram d Diagrams 9c and 9d. 6

7 1. #include <iostream> 2. using namespace std; 3. a; 4. b; 5. p(& a) 6. { p=2; 7. a=0; 8. b=1; 9. return p; 10. } 11. void q(void) 12. { static b=4; 13. a=3; 14. } 15. main() 16. { a=p(a); q(); 17. return 0; 18. } Figure 10. C++ Program for questions 10, 11, and What is the lifetime of variable b declared on line 12? a. Storage for variable b is allocated when function q is called and its storage is reclaimed when function q returns. b. Storage for variable b is allocated when function main is called and its storage is reclaimed when function main returns. c. Storage for variable b is allocated at load time and reclaimed when the program in figure 10 returns control to the operating system. d. Storage for variable b is allocated during translation and reclaimed when the file containing executable form of the program in figure 10 is deleted. 11. What is the lifetime of variable p declared on line 6? a. Storage for variable p is allocated when function p is called and its storage is reclaimed when function p returns. b. Storage for variable p is allocated when function main is called and its storage is recla imed when function main returns. c. Storage for variable p is allocated at load time and reclaimed when the program in figure 10 returns control to the operating system. d. Storage for variable p is allocated during translation and reclaimed when the file containing executable form of the program in figure 10 is deleted. 12. What is the lifetime of variable b declared on line 4? a. Storage for variable b is allocated when function q is called and its storage is reclaimed when function q returns. b. Storage for variable b is allocated when function main is called and its storage is reclaimed when function main returns. c. Storage for variable b is allocated at load time and reclaimed when the program in figure 10 returns control to the operating system. d. Storage for variable b is allocated during translation and reclaimed when the file containing executable form of the program in figure 10 is deleted. 7

8 #include <iostream> using namespace std; void swap(& m,& w){ b=m;m=w;w=b;} main() { a(1),b(2); swap(a,b); return 0; } Figure 13. C++ Program for question Select all valid characterizations of parameter m? a. Parameter m is an alias of variable a. b. Parameter m is a dangling reference. c. Parameter m is garbage. d. Parameter m contains the address of variable a while function swap is active. 1. #include <iostream> 2. using namespace std; 3. main() 4. { * a=new ; 5. * b=a; 6. delete b; 7. return 0; 8. } Figure 14. C++ Program for question Select all valid characterizations of variable a? a. On line 7 of figure 14, variable a contains the address of unnamed eger storage. b. On line 7 of figure 14, variable a is a dangling reference. c. On line 7 of figure 14, variable a references garbage. d. On line 7 of figure 14, variable a is an alias of variable b. 1. #include <iostream> 2. using namespace std; 3. main() 4. { * a; 5. a=new ; 6. a=new ; 7. return 0; 8. } Figure 15. C++ Program for question Select all valid statements? a. On line 6 of figure 15, a dangling reference is created. b. On line 6 of figure 15, an alias is created. c. On line 6 of figure 15, garbage is created. d. On line 6 of figure 15, a polymorphic reference to dual memory locations is created. 8

9 #include <iostream> using namespace std; double min( a, b){return (double)a<b?a:b;} double min( a,double b){return (double)a<b?a:b;} double min(double a, b){return (double)a<b?a:b;} double min(double a,double b){return (double)a<b?a:b;} main() { cout << min(1,2.); return 0; } Figure 16. Program for question Which C++ function min is called in function main? a. double min( a, b){return (double)a<b?a:b;} b. double min( a,double b){return (double)a<b?a:b;} c. double min(double a, b){return (double)a<b?a:b;} d. double min(double a,double b){return (double)a<b?a:b;} 17. Which C++ declaration(s) matches set T I R C = where I is the set of egers implemented on computer S, R is the set of floating-po numbers implemented on computer S, and C is the set of characters implemented on computer S? a. struct T { i;double d;char c;}; b. struct T {double d; i;char c;}; c. type T = record i:eger;r:real;c:char end; d. type T = record r:real;i:eger; c:char end; 18. Which set definitions match the Pascal type definition type T = 1..10; a. = { t I 1 t 10} b. T {( i, r) i I, r R} numbers c. = { t I 1 t < 10} d. = { t I 11 > t > 0} T where I is the set of egers = where I is the set of egers and R is the set of floating-po T where I is the set of egers T where I is the set of egers 19. In which of the following C++ code fragments is variable x assignment-compatible to variable y? a. double (*x)(); double (*y)(); b. * x=new [10]; * y=new [20]; c. enum {blue} x; enum {red } y; d. class T { i;double d;}; T x; T y; 20. Which C++ declaration(s) matches set L C L characters? a. union L {char c; L* p;}; b. class L {char c; L* p;}; c. struct L {char c; L* p;}; d. typedef L {char c; L* p;}; = {} where {} is the empty set and C is the set of 9

10 21. Which kind of type checking makes type X equivalent to type Y? type X = array[1..10] of eger; type Y = array[1..10] of eger; a. static b. dynamic c. structural d. polymorphic 22. Select the explicit type conversions that are implied in C++ for the statements: x(1); x=2+x/2.3; a. x(1); x=2+x/()2.3; b. x(1); x=(double(2)+double(x)/2.3); c. x(1); x=2+x/(2.3); d. x(1); x=()((double)2+(double)x/2.3); template <class T> class Stack { size; tos; T* S; public: struct StackException {StackException(char* m){cout << endl << Stack << m;}}; //... }; Figure 23. template class Stack implemented as a dynamically allocated array. 23. Consider the partially completed definition of template class Stack in figure 23. Which of the following are correct implementations of member function IsFull for a stack that is implemented using a dynamically allocated array? a. void IsFull(void){return size<tos;} b. bool IsFull(void){return size-1<=tos;} c. bool IsFull(void){return tos>=size-1;} d. bool IsFull(void){return tos>size;} 24. Consider the partially completed definition of template class Stack in figure 23. Which of the following are correct implementations of member function Push for a stack that is implemented using a dynamically allocated array? a. void Push(T v) { if (IsFull()) throw StackException( Full ); S[++tos]=v; } b. void Push(T v) { if (IsFull()) throw StackException( Full ); tos+=1; S[tos]=v; } 10

11 c. void Push(T v) { if (IsFull()) throw StackException( Full ); tos++; S[tos]=v; } d. void Push(T v) { if (IsFull()) throw StackException( Full ); tos=tos+1; *(S+tos)=v; } + + j * to i [] * [] * j a i * Figure 25. Attributed expression tree for question What C++ expressions are represented by the attributed expression tree in figure 25? a. a[i][j]+i+j b. a[i,j]+i+j c. a[i + j]+i+j d. *(a+4*(i+j))+i+j / * Figure 26. Expression tree for question What is the infix form of the expression given by the expression tree shown in figure 26? a. 7+6*5/4-3 b. / * c. (7+6)*5/(4-3) d * / 11

12 27. What is the prefix form of the expression given by the expression tree shown in figure 26? a *5 / b. / * c * / d * 5/ What is the postfix form of the expression given by the expression tree shown in figure 26? a * / b. 7+6*5/4-3 c. / * d. (7+6)*5/(4-3) 29. Evaluate the expression 3+6/2. Mark selection a if figure 29a contains the correct answer. Mark selection b if figure 29b contains the correct answer. Mark selection c if figure 29c contains the correct answer. Mark selection d if figure 29d contains the correct answer. expression expression + term expression + term / factor expression + term / 2 expression + factor / 2 expression + 6 / 2 term + 6 / 2 factor + 6 / / 2 Figure 29a. Answer for question Figure 29b. Answer for question / 6 2 Figure 29c. Answer for question 29. expression expression + term term term factor / factor factor Figure 29d. Answer for question

13 30. Select the grammars shown in figures 30a, 30b, 30c, and 30d that are ambiguous? Mark selection a if the grammar of figure 30a is ambiguous. In a similar way, mark selections b, c, and d, if the grammars of figures 30b, 30c, and 30d, respectively, are ambiguous. expression fi expression operation expression expression fi ( expression ) expression fi - expression expression fi id operation fi + operation fi - operation fi * operation fi / operation fi ^ Figure 30a. Grammar for question 30. expression fi operation expression expression expression fi id operation fi + operation fi - operation fi * operation fi / operation fi ^ Figure 30b. Grammar for question 30. expression fi expression expression operation expression fi id operation fi + operation fi - operation fi * operation fi / operation fi ^ Figure 30c. Grammar for question 30. expression fi term expression fi term addop expression term fi factor term fi factor mulop term factor fi power factor fi power powop factor power fi ( expression ) power fi - power power fi id addop fi + addop fi - mulop fi * mulop fi / powop fi ^ Figure 30d. Grammar for question

14 31. Select the grammar(s) that can produce the sentence given in figure 31. Mark selection a if the grammar of figure 30a can be used to produce the sentence. In a similar way, mark selections b, c, and d, if the grammars of figures 30b, 30c, and 30d, respectively, can be used to produce the sentence. id + id * id Figure 31. Sentence for question Mark the selections that satisfy the relation given in figure 32a for the grammar of figure 32b. Function p(op) returns the precedence of the argument. op Argument op is an operator in the grammar given in figure 32b. The operators given in the grammar of figure 32b include +, -, unary -, *, /, and ^. The operator, unary-, appears in production 8 p( op1) p( op2 ) L p( opn ) opi { +,,*, /,^, unary } a. p( + ) p( ) p(*) p(^ ) b. p( + ) p( unary ) p(*) p (^ ) p(*) p(/) p( d. p ( unary ) p( ) p( + ) c. ) Figure 32a. Relation for question expression fi term 2 expression fi term addop expression 3 term fi factor 4 term fi factor mulop term 5 factor fi power 6 factor fi power powop factor 7 power fi ( expression ) 8 power fi - power 9 power fi id 10 addop fi + 11 addop fi - 12 mulop fi * 13 mulop fi / 14 powop fi ^ Figure 32b. Grammar for question Mark the selections that correctly specify the association of the operators in the grammar of figure 32b. a. All the operators except unary- associate to the left and unary- associates to the right. b. All the operators associate to right. c. All the operators associate to the left. d. All the operators associate to the left except unary- and ^ which associate to the right. 14

15 34. Mark the selections that are equivalent to the C++ expression given in figure 34. if (x!=0&&x% y==0) Figure 34. C++ expression for question 34. Language Expression a. Pascal if x<>0 and x mod y = 0 then b. Ada if x/>0 and then x mod y = 0 then c. Java if (x!=0&x% y==0) d. ML if x<>0 andalso x mod y=0 then 35. Select the gra mmars shown in figures 35a, 35b, 35c, and 35d that are ambiguous? Mark selection a if the grammar of figure 35a is ambiguous. In a similar way, mark selections b, c, and d, if the grammars of figures 35b, 35c, and 35d, respectively, are ambiguous. 1 statement fi if expression then statement 2 statement fi matched-statement 3 matched-statement fi if expression then matched-statement else statement 4 matched-statement fi other Figure 35a. Grammar for question statement fi if expression then statement 2 matched-statement fi if expression then matched-statement else statement 3 statement fi other 4 matched-statement fi other Figure 35b. Grammar for question statement fi matched-statement 2 statement fi unmatched-statement 3 matched-statement fi if expression then matched-statement else matched-statement 4 matched-statement fi other 5 unmatched-statement fi if expression then statement 6 unmatched-statement fi if expression then matched-statement else statement Figure 35c. Grammar for question statement fi if expression then statement 2 -statement fi if expression then statement else statement 3 statement fi other Figure 35d. Grammar for question

16 36. Select the program fragment that is equivalent to the C++ fragment given in figure 36. for ( i=0;i<size;i++)sum+=a[i]; Figure 36. C++ Program fragment for question 36. Language Program fragment a. Pascal for i:=0 to size-1 do sum:=sum+a[i]; b. Ada for i in 0..size-1 loop sum:=sum+a(i); end loop; c. C++ i=0; while (i<size;) { sum+=a[i];i++} d. C { i=0; for(;;){if (i<size) break;sum+=a[i];i++;}} void swap( a, b) { temp; temp = a; a = b; b = temp; } main() { value = 2; list[5] = {1, 2, 3, 4, 5}; swap(value, list[value]); } Figure 37. C++ Program for questions 37 and What are the values of variable value and eger array list after function swap returns assuming such values were passed by name? Please find the relevant code in figure 37. a. value = 2, list = {1, 2, 3, 4, 5}. b. value = 2, list = {1, 2, 3, 4, 5}. c. value = 3, list = {1, 2, 3, 2, 5}. d. value = 3, list = {1, 2, 2, 4, 5}. 38. What are the values of variable value and eger array list after function swap returns assuming such values were passed by value-result? Please find the relevant code in figure 37. a. value = 2, list = {1, 2, 3, 4, 5}. b. value = 2, list = {1, 2, 3, 4, 5}. c. value = 3, list = {1, 2, 3, 2, 5}. d. value = 3, list = {1, 2, 2, 4, 5}. 16

17 program q39; var c:eger; procedure P(i:eger); procedure Q(j:eger); begin{q} if c>0 then begin writeln('c=',c); c:=c-j; Q(j-1) end end{q}; begin{p} c:=i; Q(5); end{p}; begin{q39} P(15) end{q39}. Figure 39. Pascal program for questions 39, 40, and How many activation record (stack frames) are on the activation record stack when program q39 shown in figure 39 prs c=6? a. 5 b. 4 c. 3 d How many static links must be traversed in program q39 from procedure Q to access the activation record in which variable c is allocated? a. 5 b. 4 c. 3 d How many activations of procedure Q are present when program q39 prs c=3? a. 5 b. 4 c. 3 d Historically, in the programming language FORTRAN, arguments were passed a. by reference b. by value c. by name d. by value-result 17

18 INTEGER COUNT, INC COUNT=1 INC=2 CALL EXP(COUNT+INC) END SUBROUTINE EXP(A) INTEGER A A=A+1 RETURN END Figure 43. FORTRAN program for question How is the argument, COUNT+INC, passed to parameter A in SUBROUTINE EXP? Please refer to figure 43. a. The value of the expression, COUNT+INC, is computed and assigned to parameter A. b. The address of the expression, COUNT+INC, is assigned to parameter A. c. Storage for a temporary eger is allocated in the activation record of SUBROUTINE EXP. The value of the expression is assigned to the temporary and the address of the temporary is assigned to parameter A. d. Storage for a temporary eger is allocated in the activation record of the main program. The value of the expression is assigned to the temporary and the address of the temporary is assigned to parameter A. 44. Which programming language environments require a static (lexical) link? a. Lisp b. C. c. Java. d. Pascal. 45. What programming language environments require garbage collection? a. Lisp b. C. c. Java. d. Pascal. 46. What programming languages contain constructs that support exceptions? a. Lisp b. C. c. Java. d. Pascal. 47. Garbage collection is required because a. the aggregate total of free store is insufficient to support program execution. b. operations that reclaim storage, such as delete, do not address garbage and dangling reference. c. programmatic methods are required to coalesce and compact blocks of memory on the free list. d. reference counting does not adequately reclaims storage having circular references. 48. What programming languages employ prefix notation? a. Lisp b. C. c. Java. d. Pascal. 18

19 49. What programming languages employ infix notation? a. Lisp b. C. c. Java. d. Pascal. 50. What programming languages restrict parameter passing mechanisms to pass-by-value? a. Ada b. C. c. Java. d. Pascal. 19