Homework Assignment #1

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Avice Lambert
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1 CISC 2200 Data Structure Fall, 2016 Homework Assignment #1 1 The mistery of lossing one cent. Please refer to the lab1 instruction for an example floating value ($2.34), and how the cents part extracted does not match. Rewrite the program so that you can try other floating values (such as 19.9, 7.34, 4.25,...). Also could you find out the third decimal digit, the fouth decimal digit of the floating value? This will help explain/confirm our hypothesis that 2.34 is approximated by int main() double dollar=2.34; int d,c; d = dollar; c = (dollar-d)*100; cout <<"d="<<d<<";c="<<c<<endl; 2 Local variables that have static storage duration (i.e., a lifetime that lasts until the end of the program). In class, we differentiate the scope and lifetime of variables. The former refers to the part of the codes where we can access the variable by its name. The latter refers to the duration of time when the variable exists. Usually, local variables have local scope (can be accessed by name only from the function) and automatic lifetime (meaning that it is created when the function is called, and destroyed when the function ends automatically). And usually global variables (can be accessed by name in the entire program/file) have global scope and static lifetime (meaning that it will exist until the end of the program s execution.) But we can actually use static local variable which will have static lifetime and local scope. A common usage of such variables are to keeping track of the number of times the function is called, or other quantities that we want to maintain across different calls to the function. Test (or write your own) the following function to understand/demo the usage of static local variable. You can implement the above idea of counters, or other usage that you think of. Does the address of count changed across different calls to the function? How about variable b? Does the value of b persist between subsequent calls to the function?

2 void SomeFunction(int a) static int count=0; double b; count++; cout <<"SomeFunction called for the "<<count<<" times!\n"; cout <<"address of count" << &count<<endl; cout <<"address of b" <<&b<<endl; cout <<"b="<<b<<endl; b=1.0; cout <<"b="<<b<<endl; void SomeFunctionA() int i=2; SomeFunction (i); int main() for (int i=0;i<3;i++) SomeFunction(i); int value, sum; SomeFunctionA(); 3 Passing and Returning arrays from functions. 2

3 (a) Finish the following function based on the comment. Could/should you make the array parameter a const parameter? /* * Find and return the largest value stored in an int array of a given a: the int size: the length of the array array a [0...size-1] has been initialized with int the largest value in a[0...size-1] is the largest value stored in the array a */ (b) Finish the following code s todo: /* A function that reads a sequence of integers from input (with the length of sequence, follow For example, if the length is 3, and the numbers are then the array returned will be of size 3, and stores values 123, 345, and length: upon return, stores the length/size of the the pointer pointing to the array */ int * ReadNumberSequence (int & size) int * array = NULL; // initialize the pointer to NULL do cout <<"Enter the length of the number sequence:"; cin >> size; while (size<=0); // Todo: Write a statement to allocate memory for the array. // Note: we only know the value of size at run time, so we need to DYNAMICALLY // allocate memory for this array 3

4 // Todo: write a loop to read size # of int from input, and save them to the array return array; int main() // Todo: delcare necesssary variables //Todo: call the ReadNumberSequence function to read a sequence of numbers //Todo: write a loop to display the elements in the array returned... //Todo: free the array returned by ReadNumberSequence. 4 Address and sizeof variables. Recall the sizeof function returns the size of a variable (i.e., the number of bytes used by a variable). Type a C++ program as necessary to help you answer the following questions: N ote when you cout a pointer variable or value, it will be shown in hexadecimal, as indicated by the 0X prefix of the number. You can cast the pointer to long if you want the address to be displayed in decimal. int a=10; // the size of a is: double d=3.1415; // the size of d is: char c= A ; // the size of c is: int * p = NULL; // the size of p is:. // the value of p is: double * q=null; // the size of q is: 4

5 // the value of q is: char * t=null; // the size of t is:, the value of t is: p = &a; q = &d; t = &c; // the value of p is // the value of q is // the value of c is cout << *p << endl; // This displays. When accessing *p, the following bytes are // accessed: (give a range of memory) cout << *q << endl; // This displays. When accessing *q, the following bytes are // accessed: (give a range of memory) cout << *t << endl; // This displays. When accessing *t, the following bytes are // accessed: (give a range of memory) cout << "p+1=" << p+1 << endl; // How much is p differs from p+1? cout << "q+1=" << q+1 << endl; // How much is q differs from q+1? cout << "t+1=" << t+1 << endl; // How much is t differs from t+1? // We observe that all pointer variables are of the same size, but we need to differentiate // a pointer to an int against a pointer to a double, because: 5 Memory map. For the following code, draw the memory map to illustrate the variables and pointers after each statement that is labelled with numbers. int a=100; int *p=&a; // (1) 5

6 int *q= new int; // (2) *q = 3; // (3) *p = *q; // (4) char str[20]="hello"; char * r = str; // (5) *r = H ; // (6) r++; *r = E ; // (7) 6

Homework Assignment #2 (revised)

CISC 2000 Computer Science II Fall, 2018 1 Recall the following functions and operators: Homework Assignment #2 (revised) sizeof function: returns the size of a variable (i.e., the number of bytes used