C++ Programming for Experienced Engineers/

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File IO of Numeric and String Data

File IO of Numeric and String Data

Understand the file handling of Numeric and String data in C++.

We'll cover the following...

Challenge

Write a program to write numeric and string data into a file called SAMPLE.TXT. Read the same file back and display the contents read on the screen.

Sample run

root@educative:/usr/local/educative# g++ main.cpp 
root@educative:/usr/local/educative# ./a.out 
Z
25
473.14
Hyperbole!
root@educative:/usr/local/educative# cat SAMPLE.TXT
Z
25
473.14
Hyperbole!

Coding exercise

Your job is to write the code for writing and reading to the file in the main( ) function.

// File IO of numeric and string data
#include <fstream>
#include <iostream>

int main( ) 
{ 		
	char ch = 'Z' ; 	
	int i = 25 ; 	
	float a = 473.14f ; 	
	char str[ ] = "Hyperbole!" ; 
	
	// Your code goes here

	//  send data to screen 	
	std :: cout << ch << std :: endl ;
	std :: cout << i << std :: endl ; 
	std :: cout << a << std :: endl ;
	std :: cout << str << std :: endl ;
	
	return 0 ; 
}

Coding solution

The following code widget has the solution for the challenge explained above.

// File IO of numeric and string data
#include <fstream>
#include <iostream>

int main( ) 
{ 		
	char ch = 'Z' ; 	
	int i = 25 ; 	
	float a = 473.14f ; 	
	char str[ ] = "Hyperbole!" ; 
	
	// create file for output 	
	std :: ofstream outfile ( "SAMPLE.TXT" ) ;  	

	// send data to file 	
	outfile << ch << std :: endl ;
	outfile << i << std :: endl ;
	outfile << a << std :: endl ;
	outfile << str << std :: endl ;
	
	outfile.close( ) ;

	std :: ifstream infile ( "SAMPLE.TXT" ) ;

	//  read data from file 	
	infile >> ch >> i >> a >> str ;

	//  send data to screen 	
	std :: cout << ch << std :: endl ;
	std :: cout << i << std :: endl ; 
	std :: cout << a << std :: endl ; 
	std :: cout << str << std :: endl ;
	
	return 0 ; 
}

Explanation

The contents of the file are displayed on the console using the cat command followed by the filename, like this:

cat SAMPLE.TXT

To begin with, we have defined an object called outfile, of type ofstream ...