file_io1.cpp

#include <string>// for strings
#include <iostream>// for I/O
#include <fstream>// for file I/O
#include <iomanip>// for setw()
#include <cstdlib>// for exit()
using namespace std;

// forward declarations
void writeCharsetToFile (const string& filename);
void outputFile (const string& filename);

int main () {
  writeCharsetToFile("charset.out");
  outputFile("charset.out");
}

void writeCharsetToFile (const string& filename) {
// open output file
  ofstream file(filename);
// file opened?
  if (! file) {
// NO, abort program
    cerr << "can’t open output file \"" << filename << "\""
	 << endl;
    exit(EXIT_FAILURE);
  }
// write character set
  for (int i=32; i<256; ++i) {
    file << "value: " << setw(3) << i << "  "
	 << "char: " << static_cast<char>(i) << endl;
  }
}// closes file automatically

void outputFile (const string& filename) {
  // open input file
  ifstream file(filename);
  // file opened?
  if (! file) {
    // NO, abort program
    cerr << "can’t open input file \"" << filename << "\""
	 << endl;
    exit(EXIT_FAILURE);
  }
  // copy file contents to cout
  char c;
  while (file.get(c)) {
    cout.put(c);
  }
}// closes file automatically