Can someone help me to make my program sort according to the average gallons used per car I keep geting 30 - 40 error when i try to compile it. Also

my files do exist.

Code:

#include <fstream>
#include <iostream>
#include <iomanip>
using namespace std;
const int MAXCARS = 12;
float avgallons = 0;
int numel = 0;
float totalmiles, totalgallons;
struct Car
{
int number, miles;
float gallons;
float averagegallons;
}Cars;
Car Cars[MAXCARS];
void getdata(int, int, float);
void processdata(int, float);
void sort(float);
void putdata(int, float);
ifstream HopeData;
ofstream MikeData;
void main()
{
HopeData.open("gdata.dat");
MikeData.open("pdata");
if(HopeData.fail())
{
cout << "\n\nFile not successfully opened\n\n";
}
cout << "\n\nFile successfully opened\n\n";
MikeData << "\n\n Car Report" << endl;
MikeData << "Number Average Per Car" << endl;
cout << setiosflags(ios::showpoint);
cout << setiosflags(ios::fixed);
cout << setprecision(2);
getdata(Cars.number, Cars.miles, Cars.gallons);
putdata(Cars.number, Cars.averagegallons);
MikeData << "\n\nAverage Gallons Used by All Cars is " << avgallons << endl;
}
void getdata(int number, int miles, float gallons)
{
while(HopeData.peek() != EOF)
{
HopeData >> Cars.number >> Cars.miles >> Cars.gallons;
HopeData.ignore(80,'\n');
processdata(Cars.miles, Cars.gallons);
}
}
void processdata(int miles, float gallons)
{
Cars.averagegallons = Cars.miles / Cars.gallons;
totalmiles = totalmiles + Cars.miles;
totalgallons = totalgallons + Cars.gallons;
avgallons = totalmiles / totalgallons;
numels++;
sort(Cars.averagegallons);
}
void sort(float averagegallons, int numels)
{
int i,j,min,minidx,temp,moves=0;
for(i=0;i<numels;i++)
{
min = Cars[i];
minidx = i;
for(j=i+1;j<numels;j++)
{
if(Cars[j].averagegallons<Cars[i].averagegallons)
{
min = Cars[j];
minidx=j;
}
if(min<Cars[i].averagegallons)
{
temp=Cars[i];
Cars[i]=min;
Cars[minidx]=temp;
}
}
}
}
void putdata(int number, float averagegallons)
{
while(HopeData.peek() != EOF)
{
MikeData << Cars[].number << "\t " << Cars[].averagegallons << endl;
}
}