School of Information Technology and Computer Science CSCI192 - Spring Session Revision

Transcription

1 School of Information Technology and Computer Science CSCI192 - Spring Session Revision Aim: Revision 1. Covert 0x27 from hexadecimal into 8-bit binary value Convert bit binary value into its hexadecimal representation 0x36 Hexadecimal Binary A 1010 B 1011 C 1100 D 1101 E 1110 F Assuming the following declaration char volt1 = 70, volt2 = 90, result; What is the result of the following expression (in the decimal representation)? result = volt1 + volt2; (A) 70 (B) 90 (C) 160 (D) 0 4. Assuming the following declaration int length = 25, newlength; What is the result (in the decimal representation) of the following expression? newlength = length << 2; (A) 100 (B) 50 (C) 25 (D) 0

2 5. Assuming the following declaration int code = 9, newcode; What is the result (in the decimal representation) of the following expression? newcode = code >> 3; (A) 2 (B) 4 (C) 64 (D) 1 6. Assuming the following declaration unsigned char statuscode = 0x2F, mode; What value is assigned to the variable mode? if( (statuscode & 2)!= 0 ) mode = 1; else mode = 0; (A) F (B) 2 (C) 1 (D) 0 7. In which segment of the application memory space are un-initialised local automatic variables placed? (A) (B) (C) (D) (E) The Heap The Stack The Initialised Data The Un-initialised Data None of the above

3 8. Considering the following declaration of an array float itemprice[size]; Which of the pointers declared below can be used to access elements of the array without explicit type casting? (A) (B) (C) (D) (E) char *ptra; float *ptrb; float **ptrc; double *ptrd; None of the above 9. What is the output of the following C code fragment assuming that memory is allocated correctly? int i, *ptri; ptri = malloc( 10*sizeof(int) ); for(i=0; i<10; i++) ptri[i] = i*2 +1; printf("%d \n", *(ptri+9)); free(ptri); (A) 19 (B) 10 (C) 9 (D) %d \n 10. Considering the following declarations #define BUFSIZE 1024 int buffer[bufsize]; Which of the following functions can be used to release memory reserved by buffer when it is not needed any longer? (A) free(buffer); (B) clear(buffer); (C) fflush(buffer); (D) realloc(buffer);

4 11. Suppose an algorithm has a complexity of O(NlogN). Such an algorithm is called a(n) algorithm (A) polynomial (B) exponential (C) linear (D) linear logarithmic (E) logarithmic 12. Consider the following class definition: class File{ private: FILE *fp; public: File(const char *filename, const char *mode) { fp = fopen(fn, mode); if (fp == NULL) throw "Can t open file"; FILE *getfp(){ return fp; ~File(){fclose(fp); ; Which of the following calls to create the object File is correct? (A) File fout("test1.dat", "w"); (B) File fout("w"); (C) File *fp = new File(); (D) File fout("test1.dat"); 13. What is the result of evaluating the expression below? static_cast<int>(4.9 + static_cast<double>(7/2)) (A) 4 (B) 8.4 (C) 7.9 (D) Provide an example of a 1D static array declaration and a corresponding pointer, which can be used for accessing array elements. How to obtain an address of the element with index 4 and assign it to the pointer? int myarray[256], *iptr; iptr = &myarray[25];

5 15. What are major rules of the pointer arithmetic? Can you add two pointers of the same type? No. Can you add a pointer and a constant? Yes. How the pointer type affects the result? Increment of pointer value is by size of its type. Can you subtract two pointers of the same type? Yes. Can you use relational operators with pointers? Yes. 16. What is dynamic memory allocation? This is to ask the operating system to reserve some memory. Access to the reserved memory is exclusive. This means that that the current program has exclusive right to access the allocated range of bytes. No other program is allowed to access the same range of memory. How to allocate a dynamic array sufficient for storing a nul terminated c-string "Hello". 6 bytes as space is needed for the trainling nul character. Provide an example. char *cptr; cptr=malloc((strlen( Hello )+1) * sizeof(char)); strcpy(cptr, Hello ); 17. Which C-string functions from string.h library can be used: to obtain length of a string: strlen(char *cptr) to compare two strings: strcmp(char *s1, char *s2); to concatenate two strings: strcat(char *s1, char *s2); 18. How to release a dynamically allocated memory block? Either with free(void *) or delete(void *) depending on whether the memory was allocated by one of the malloc functions or new. 19. What is sorting? Create a total order amongst elements in an array. How the bubble sort algorithm works? BubbleSort works by repeatedly stepping through the list of elements in an array to be sorted, comparing each pair of adjacent items in the array and swapping them if they are in the wrong order. The pass through the list is repeated until no further swaps are needed, which indicates that the list is sorted. What is its computational complexity? O(n*n), quadratic 20. Consider the following declarations. class myclass { public: void print() const; myclass(); myclass(int, double); private: int u; double w; ;

6 myclass howdy; -How many data members does class myclass have? 2 -How many private members does class myclass have? 2 -Write a C++ statement that declares an object t of type myclass, and initializes the data members to 45 and respectively myclass t(45, 86.24); 21. The following C++ program that implements and uses a class stack causes a compilation error: no matching function for call to stack::stack( ) (i) The compilation error refers to a missing function. What is the name of such a function in a class implementation? It is the default constructor function for the class stack. (ii) Write C++ code to implement the missing function so that the data members of the class stack are initialized as follows: top = EMPTY; max_len = 15; the char variable s holds 15 elements. stack::stack() { top = EMPTY; max_len = 15; s = new char[15]; (iii) Write the constructor that is to be called when a declaration stack data(8); is encountered in a program. stack::stack(int size) { top = EMPTY; max_len = size; s = new char[size]; (iv) After fixing the compilation error, what will be the output of the program? The output will be: 291CSC #include <iostream> using namespace std;

7 class stack { private: const int EMPTY = -1; char *s; int max_len; int top; public: stack(int size){ s = new char[size]; max_len = size; top = EMPTY; void push(char c){s[++top] = c; char pop(){return(s[top--]); char top_of() const {return (s[top]); bool empty() const {return(top == EMPTY); bool full() const {return(top == max_len-1); ; int main() { stack data; char info[8] = "CSCI192"; for (int i = 0; i < strlen(info); ++i)[ data.push(info[i]); while(!data.empty()){ cout << data.pop(); cout << endl; return 0;