How do I write this program into a text file

Question

#include <iostream>

#include <fstream>

#include <string>

#include <cstring>

#include <cstdlib>

#include <iomanip>

using namespace std;

// global declarations for constants

const int MAX_ANSWERS = 20;

const int MAX_STUDENTS = 200;

const int MAX_SCORE = 40;

// function prototypes

void readDataFromFile(string fileName, string *correctAnswers, string *studIDs, string *studAnswers);

void computeStudScores(string correctAnswers, string* studAnswers, double *studscores);

void computeStudGrades(double *studscores, char *studgrades);

void displayOutput(string *studIDS, string *studAnswers, double *studscores, char *studgrades);

// global declarations for a variable

int studentsCounter = 0;

// start main function

int main()

{

// variables declaration

fstream outfile;

string fileName;

string correctAnswers;

string *studIDS = new string[MAX_STUDENTS];

string *studAnswers = new string[MAX_STUDENTS];

double *studScores = new double[MAX_STUDENTS];

char *studGrades = new char[MAX_STUDENTS];

outfile.write("studentAnswers.txt", ios::out | ios:: app);

// invoke the function readDataFromFile()

readDataFromFile(fileName, &correctAnswers, studIDS, studAnswers);

// invoke the function compute_Stud_Scores()

computeStudScores(correctAnswers, studAnswers, studScores);

// invoke the function compute_Stud_Grades

computeStudGrades(studScores, studGrades);

// invoke the function displayOutput

displayOutput(studIDS, studAnswers, studScores, studGrades);

outfile.close();

return 0;

}

// readDataFromFile() function accepts a string, string reference, string array, and string array

void readDataFromFile(string fileName, string *correctAnswers, string *studIDs, string *studAnswers)

{

// declare the required variables

ifstream inFile;

string line;

int position;

int index;

// open the file

inFile.open("student_test.txt");

// condition to check if the inFile does not exists

if (!inFile)

{

//display an error message and exit from the program

cout << "Unable to open the file \"" << fileName << "\""

<< endl;

} // end if

// read the correct answers from the file

getline(inFile, *correctAnswers);

// set the index to 0

studentsCounter = 0;

// get the next line

getline(inFile, line);

index = 0;

// loop until there are no more lines in the file

while (inFile)

{

// find the position of " " in the line

position = line.find_first_of(" ");

// substring the line and get the student ID

studIDs[index] = line.substr(0, position);

// substring the line and get the student answers

studAnswers[index] = line.substr(position + 1);

// increment the index

index++;

// get the next line

getline(inFile, line);

}

// close the file

inFile.close();

studentsCounter = index;

}

// compute_Stud_Scores function that accepts string variable, string array, and double array

void computeStudScores(string correctAnswers, string* studAnswers, double *studscores)

{

// declare the required variables

string student_Ans;

double scoreStud;

// loop through each student

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

{

// retrieve the student answers present at index i

student_Ans = studAnswers[i];

// set the score of the student to 0 initially

scoreStud = 0;

// loop through each answer

for (int j = 0; j < student_Ans.length(); j++)

{

// check whether the character at j of student_Ans is blank

if (student_Ans.at(j) == ' ')

{

// add 0 score to the current answer

scoreStud = scoreStud + 0;

}

// otherwise, check if student_Ans is equal to the

// correctAnswers

else if (student_Ans.at(j) == correctAnswers.at(j))

{

// if correct, add +2 to the existing score

scoreStud = scoreStud + 2;

}

// otherwise, check if student_Ans is not equal to the

// correctAnswers

else

{

// if wrong, add -1 to the score

scoreStud = scoreStud - 1;

}

}

// now set the score of the student in stud_scores array

studscores[i] = scoreStud;

}

}

// compute_Stud_Grades() function that accetps a string, array of strings and double

// array

void computeStudGrades(double *studscores, char *studGrades)

{

// declare the required variable

double studpercent;

// loop through each student scores

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

{

// compute the average score of the student in terms of

// percentages

studpercent = (studscores[i] / MAX_SCORE) * 100;

// depending on the stud_percent, set the grade of the

// student

// if the stud_percent is within the range of 90 - 100

// set the grade to A

if ((studpercent >= 90) && (studpercent <= 100))

{

studGrades[i] = 'A';

}

// if the stud_percent is within the range of 80 - 89.99

// set the grade to B

else if ((studpercent >= 80) && (studpercent <= 89.99))

{

studGrades[i] = 'B';

}

// if the stud_percent is within the range of 70 - 79.99

// set the grade to C

else if ((studpercent >= 70) && (studpercent <= 79.99))

{

studGrades[i] = 'C';

}

// if the stud_percent is within the range of 60 - 69.99

// set the grade to D

else if ((studpercent >= 60) && (studpercent <= 69.99))

{

studGrades[i] = 'D';

}

// if the stud_percent is within the range of 0 - 59.99

// set the grade to F

else

{

studGrades[i] = 'F';

}

}

}

// displayOutput() function accepts two string arrays, one double array, and a character array.

void displayOutput(string *studIDS, string *studAnswers, double *studscores, char *studgrades)

{

// display the header

cout << "Students Results:" << endl;

cout << "Student ID\tStudent Answers\t\tScore\tGrade" << endl;

cout << "-----------------------------------------------------" << endl;

cout << setprecision(2) << fixed;

// loop through each student

// display the result

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

{

cout<< studIDS[i] << "\t" << studAnswers[i] << "\t" << studscores[i] << "\t" << studgrades[i] << endl;

}

}

Answer 1

Hello, Ethan O.,

It's not immediately clear what you mean with your question "how do I write this program into a text file". We software-types tend to be kind of literal in our interpretation of things, so my first thought was that you wanted to put the code, above, into a file! However, after *looking* at the code, I *think* you mean "how do I get the program to write its output into a text file.

I think this because, in your main() function, you declare:

fsrteeam outfile;

then, later, you say:

outfile.write("studentAnswers.txt", ios::out | ios:: app);

and, near the end of main():

// invoke the function displayOutput

displayOutput(studIDS, studAnswers, studScores, studGrades);

outfile.close();

Now, if my guess is correct, I see at least 2 problems with your implementation.

First, the `outfile.write("studentAnswers.txt", ios::out | ios:: app);` statement doesn't do what you want, which is to open a file called "studentAnswers.txt" for output. To open the file, you have 2 choices:

1. You can open it in the declaration of outfile, as in `fstream("studentAnswers.txt", ios_base::out);`, or
2. You can open it by replacing your outfile.write() with: `outfile.open("studentAnswers.txt", ios::out);

(I left off the ios_base::app, since I suspect that you don't want to *append* to the file if it exists, but *replace* the old contents. Add it back, otherwise.)

Which ever method you choose, you should probably check that the file was opened properly, by adding some error checking, right? :-)

Second, and really the crux of your issue, is that except for closing outfile in main() with `outfile.close()`, you don't *do* anything with outfile! I *think* that you were expecting the function displayOutput() to write its output to outfile (right?), but instead, it's writing to cout (stdout, probably the console).

So, how do you fix this? As I see things, you have a couple choices.

First, you can add a new argument to displayOutput(), as in `displayOutput(fstream &outfile, ...), and supply outfile to the call; then, change all uses of cout inside displayOutput() to uses of outfile, instead.

The other possibility (perhaps not in the spirit of the assignment, but functionally the same), is remove all declarations and uses of outfile, keep the use of cout in displayOutput() and, when you run the program,

redirect stdout to a file called "studentAnswers.txt", as in:

$ ./grades > studentAnswers.txt