Name ______________________________

CPTR246 Spring '08 (100 total points) Exam 2

1. Structures: Assume that the following code appears in your program.

struct student { // defines student "type"

int ID; // student id number

double GPA; // grade point average

char name[40]; // student’s name

string courses[4]; // four courses scheduled

char email[30]; // email address

};

student Oscar = {567, 2.01, “Oscar Mayer”, “CPTR000”,

“BSKT100”, “GOOF101”, “FUN110”,

“oscar@yahoo.com” };

student * studentptr = & Oscar;

(a) For each of the following, indicate if the reference is a syntax error or not. If not, give the value of the reference? (8 points)

Reference Error? (yes or no) If no, give its value

Oscar.ID __________________ ________________________

Oscar->ID __________________ ________________________

studentptr.GPA __________________ ________________________

studentptr->GPA __________________ ________________________

(b) Using the definitions above, write a for loop that displays the courses that Oscar is scheduled for, one per line. (Do not use any string literals.) (8 points)

2. Null-terminated Character Arrays:

Use pages 453-454 of your textbook and the cctype functions at the bottom of the ASCII chart handout (which can also be found on page 1025-1026) as needed.

(a) To the right of the following code, write what would be displayed on the screen. (10 points)

#include <iostream>

using namespace std;

int main()

{

char s1[20] = "cat";

char s2[20] = "dog";

char s3[20] = "cow";

char s4[20] = "horse";

char s5[20] = "pigeon";

char s6[20] = "eagle";

strcpy(s1, s2);

cout << s1 << endl;

cout << s2 << endl;

cout << strcat(s3, s4) << endl;

cout << s3 << endl;

strncpy(s5, s6, 3);

cout << s5 << endl;

return 0;

}

(b) Circle T or F to indicate whether each of the following evaluates to true (non-zero) or false (zero), respectively. (2 points each)

char name [20]= “Oscar Mayer”;

char message[30] = “The cost is $200.00.”

T F strlen(name) == 20

T F isalpha(name[0])

T F isdigit(message[16])

T F strcmp(name, “Oscar Mayer”)

3. Pointer Basics

(a) What is a pointer? (3 points)

(b) To the right of the following code, write what would be displayed on the screen. (24 points)

#include <iostream>

using namespace std;

int main() {

int x = 78;

int y = 99;

int * oneptr;

int * anotherptr;

int tests[5] = {88, 93, 78, 99, 90};

oneptr = & x;

anotherptr = & y;

cout << * oneptr << " " << * anotherptr << endl;

x = 93;

*oneptr = 88;

cout << * oneptr << " " << * anotherptr << endl;

cout << x << " " << y << endl;

anotherptr = oneptr;

cout << * oneptr << " " << * anotherptr << endl;

cout << x << " " << y << endl;

cout << *tests << endl;

cout << *tests + 1 << endl;

oneptr = tests;

*(oneptr + 1) = 90;

for (int i = 0; i < 5; i ++)

cout << oneptr[i] << " ";

cout << endl;

return 0;

}

4. Pointer parameters (the old C way) In the following program, make all of the changes to convert the call-by-reference parameters in the function “rectangle” to be call by reference using pointer parameters (known as the old C way). (8 points)

#include <iostream>

#include <cmath>

#include <string>

using namespace std;

void rectangle(double l, double w, double & area, double & perimeter){

// pre: l and w have been given values

// post: area and perimeter of the rectangle are computed

area = l * w;

perimeter = 2 * (l + w);

}

int main() {

double length, width, area, perimeter;

cout << "Enter the length and width of your rectangle: ";

cin >> length >> width;

rectangle( length, width, area, perimeter);

cout << “area = “ << area << “ and perimeter) = “ << perimeter << endl;

}

5. You and a classmate are looking over the shoulder of an upperclassman who is testing a program called widget.exe. At the UNIX prompt you see that she types the following:

widget.exe < file1.dat

Your classmate doesn’t understand what the “< file1.dat” is for or how it works. Explain it to him. (5 points)

6. Formatting output: Write cout statements to display the following as described.

int age = 21;

double cash = 12.0;

string name = “Oscar Mayer”;

Print a line that has age right justified in a column that is 5 characters wide. (2 points)

On one line, print name left-justified in a column of width 30 followed by cash displayed with 2 decimal positions, right-justified in a column of width 8. (4 points)

7. Command Line Arguments and File Processing: (20 points)

Write a program that takes a file of real numbers as input, reads each real number, doubles it, and then writes it to an output file (one number per line). Example runs:

./doubler.exe input.dat output.dat

./doubler.exe myfile.dat yourfile.dat

Important points:

· The names of the files MUST come from the command line. If they are NOT there, end the program with an appropriate error message.

· You may assume that the file contains only real numbers.

· Do NOT open the output file if the input file did not open properly.

· You do NOT need to have more than the main function.

· You do NOT need to include any comments.

(An additional blank page has been added for your use.)