Review code - dynamic memory arrays+writing to a file

[matthematician]

Hi all-

Looking for someone to critique my code here. My objective is to write a program that opens a given file ("input.txt"), writes the file's contents to 3 dynamicallly allocated arrays (A, B, C), and create a file ("output.txt"). I wrote this while referencing the C++ Language Tutorial of this website (mostly Control Functions, Dynamic Memory, & Input/Output with Files).

I am least sure about my implementation of the arrays; ie, reading data from the opened input.txt & subsequently writing to output.txt.

Disclaimer-

I don't have internet access on my PC, & therefore cannot get a compiler. Hoping to locate a public computer with one this weekend.

Your time & feedback are appreciated.

//basic file operations
#include <iostream>
#include <ifstream>
#include <ofstream>
int main ( ) {
	ifstream myfile;
	myfile.open ("input.txt");
	if(!myfile) {
		cerr<<"Error: file could not be opened"<< endl; 
		exit(1);
		}
	else if (myfile.is_open() ) {
		int n; /*declaring n*/
		public: int Read(); /*Reads the next character from the input stream and advances the character position by one character. How do I assign this character value to int n?*/
		int A [n]; /*arrays of size n?*/ 
		int B [n];
		int C [n];
		for (int n=1; n>0; n++) /*initial n = 1, while n > 0, increment n*/ {
			int x[ ]; 
			int y[ ];
			int z [ ];
			A[n-1] = int x[n];
			B[n-1] = int y[n];
			C[n-1] = int z[n];
			}
		}
  	myfile.close( ); /* the input.txt file*/
	return 0;
	ofstream myfile;
	myfile.open (“output.txt”);
	myfile << int n << endl;
	for  (int n = 0; n < int n; n++) {
		myfile << A[n]<<B[n]<<C[n]<<endl;
		}
	result = sub ( n, A, B, C);
	myfile << result;
	myfile.close ( );
	return 0;
}

edit:The following conditional:

if(!myfile) {
 cerr<<"Error: file could not be opened"<< endl; 
exit(1);
 }

Was found in another thread.

edit: Code tags added. (Thanks, Hutch.)

[MrHutch]

The lines...

int A [n]; /*arrays of size n?*/ 
int B [n];
int C [n];

... aren't going to compile.

For an array that uses stack memory the compiler needs to know the size at compile time. However, if you're using dynamic memory, the size can be allocated at run time.

int *A = new int [n];

// Somewhere near the end of your code...
delete []A;

EDIT: I should note, for such dynamic collections I would advise using a vector instead.

Also, there's a couple of other syntactical issues with your code. Might be easy to spot if you use code tags and indentations. :-)