Question

(1) Why do several functions in iostream and fstream have identical names? When is it advantageous to reuse function names?

(2) Describe the five-step process of file I/O. Explain how to use ifstream and ofstream to open and close input and output files. Illustrate the process with the skeleton program provided in this section.

Please describe in details.

Answer 1

1.)

• The iostream and fstream classes are inherited from the parent class,istream class.
• Since C++ is a object-oriented programming language, it supports inheritance , function overloading and polymorphism features.
• The inheritance feature reduces code reusability.
• Function overloading feature to create one function with different parameter and argument list.
• The most of the functions in the iostream and fstream seems to be similar.
• The funcitons in the iostream are meant for reading and writing data from keyboard and write the data to console.
• The funcitons in the fstream are meant for reading and writing data from secondary storage memory ,hard disk and write the data to files and store in computer hard disk or seconary storage device.

2.)
Five step process of file I/O.
Step1: Include fstream header file.
Step2: Declareobject of the fstream or ostream class to read or write the data to file.
Step3: Open the file usingopen(filename) method.
Step4: Check if file exists using fail() function. If file not exists, then close the file using fclose() function
Step5: Close the file stream object using fclose() function.

Skeleton c++ program for opening input file stream for reading file and write the data to output file
stream.
#include <fstream>
using namespace std;
int main()
{
   //Open objects of ifstream and ofstream classes
   ifstream inFile;
   ofstream outFIle;
  
   //Open file for reading
   inFile.open("input.txt");
      
   //Check if file exists or not
   if (!inFile)
   {
           cerr << "Unable to open file datafile.txt";
           exit(1);   // call system to stop
   }

   //Open file for writing
   outFIle.open("output.txt");
   //Read data from file inFile and write to file output.txt
   while (inFile >> x)
   {
      outFile>>x>>endl;
   }

   //Close the file objects
   inFile.close();
   outFile.close();
   return 0;
}