C++ binary file reader

#include <iostream>
#include <iomanip>
#include <string>
#include <fstream>
#include <ios>

//
//function prototype
void PressEnterToContinue();


using namespace std;


void main(int argc, char *argv[])
{
	int n = 0; //used for prompting input file name
	int r;
	int x = 0, m = 0, a = 0;
	ifstream filename; //start filestream
	int size; //for file size
	char *file_buffer; //buffer for storing file

	//if user calls program from cmd prompt incorrectly or with "/?"
		if((argc < 2) || (strcmp(argv[1],"/?") == 0)) 
			{
				cout << "This program reads a file and prints each character as a hexadecimal\n";
				cout << "\n";
				cout << "Usage: hw5 [input filename]\n";
				exit(0);
			}
	
		//
		//prompt user for file name and continue to do so until a valid file name is given
		do
		{	
			filename.open(argv[1], ios::binary | ios::ate); //open file in binary mode
			if ( !filename )
				{
					cout << "Please enter a valid file name.\n";
					cin >> argv[1]; 
				}
			else	
				{
					n = 1; //end while loop since file is open
				}
		} while (n != 1);
		
		
		filename.seekg(0, ios::end); //seek EOF
		size = filename.tellg(); //return pointer at that position
		file_buffer = new char[size]; 
		filename.seekg(0, ios::beg); //seek beginning of file
		filename.read(file_buffer, size); //read file, up to int size, into file_buffer
		
		
		//print 20 lines in binary followed by ASCII
		do
		{
			for (int g = 0; g <= 20; g++)
			{
				
				for (x; x < 16 + a; x++)
					{
						r = file_buffer[x]; //caste cout to type int, so 'hex' can work
						cout << hex << setw(2) << uppercase << r << " ";
					}
				
				cout << "\t"; //align ASCII portion on right	
				
				for (m; m < 16 + a; m++)
					{
					//catch control character (endet/new line) and print '.' in it's place
						if (iscntrl(file_buffer[m]))
							cout << "."; 
						else	
							cout << file_buffer[m];
					}
				
				//increment a to print the next 16 bits
				a+=16;
				cout << endl;
			}
			
			//pause and wait for 'Enter' to continue
			PressEnterToContinue();

		//EOF is an int. file_buffer only stores characters. 
		//can't use file_buffer[x]		
		} while (x <= size ); 
		
		
		//
		//close file at program exit
		filename.close();
}

void PressEnterToContinue( )
 {
	cout << "Press ENTER to continue... ";
	cin.ignore( std::numeric_limits <std::streamsize> ::max(), '\n' );
 }

file_buffer[x] != EOF 

#include <iostream>
#include <fstream>

int main(int argc, char** argv)
{
    char buffer[100];
    
    std::ifstream fin ("testfile", std::ifstream::binary);
    
    fin.read(buffer, 100);
    
    std::cout << fin.gcount() << std::endl;
	
	for (size_t i = 0; i < fin.gcount(); ++i)
		std::cout << (unsigned long)buffer[i] << std::endl;
    
    fin.close();
    return 0;
}

cout << "/t";

while (x <= size )
		{
			for (int g = 0; g <= 20; g++)
			{
				
				for (x; x < 16 + a; x++)
					{
                                         if (x>size) {
                                            return 0;
                                          }
                                         else{
						r = file_buffer[x]; //caste cout to type int, so 'hex' can work
						cout << hex << setw(2) << uppercase << r << " ";
                                       }
					}
				
				cout << "\t"; //align ASCII portion on right	
				
				for (m; m < 16 + a; m++)
					{
					//catch control character (endet/new line) and print '.' in it's place
						if (iscntrl(file_buffer[m]))
							cout << "."; 
						else	
							cout << file_buffer[m];
					}
				
				//increment a to print the next 16 bits
				a+=16;
				cout << endl;
			}
			
			//pause and wait for 'Enter' to continue
			PressEnterToContinue();

		//EOF is an int. file_buffer only stores characters. 
		//can't use file_buffer[x]		
		}