crash when reading from a file - c++

Question

first of all, i'd like u to know that im a college student (our syllabus in programming is not that advanced yet)(Btw im not asking for answers to my assignments etc, im just practicing).
Ok so i have 2 problems
Some function in my code changes the value of my array (when i dont want it to)
I really have no idea, but it seems that getting some values from a file to store into my array crashes the program, furthermore, after fiddling a bit with the code (i have no idea what changed), it no longer crashes during the said part, BUT it still crashes at the end of the code execution..
i hope u guys could help me, i've been searching whole day long.
#include <iostream>
#include <fstream>
#include <string>
#include <iomanip>
using namespace std;
/* run this program using the console pauser or add your own getch, system("pause") or input loop */
void readFile (float x[], int &y) {
ifstream load;
string filename;
cout << "Enter the name of the file: ";
cin >> filename;
load.open(filename.c_str());
while (!load.eof()) {
load >> x[y];
y++;
}
if (!load) {
cout << "asd";
}
}
void computeC (float x[], int y, float z[]) {
int v=0;
for (v=0; v<=y; v++) {
z[v] = (5 * (x[v] - 32)/9);
}
}
float average (float x[], int y) {
int v=0;
float sum=0;
for (v=0; v<=y; v++) {
sum += x[v];
}
return sum / v;
}
void grade (float x[], char grades[], int y, int &hi, int &med, int &lo) {
int v=0;
hi = med = lo = 0;
for (v=0; v<=y; v++) {
if ( x[v] >= 35) {
grades[v] = 'H';
hi++;
}
else if ( (x[v] < 35) && (x[v] >= 20) ) {
grades[v] = 'M';
med++;
}
else if ( x[v] < 20 ) {
grades[v] = 'L';
lo++;
}
}
}
void writeFile (float x[], float y[], int z, char w[]) {
ofstream save;
int v=0;
for (v=0; v <= z; v++) {
cout << "C(Celcius)" << left << setw(5);
cout << "F(Farenheit)" << left << setw(5);
cout << "Description\n";
cout << right << setw(7) << y[v];
cout << left << setw(8) << x[v];
cout << left << setw(8) << w[v];
}
}
int main(int argc, char** argv) {
int ctr=0, high, medium, low;
float F[ctr], C[ctr], ave;
char grades[ctr];
readFile (F, ctr);
computeC (F, ctr, C);
ave = average (C, ctr);
grade (C, grades, ctr, high, medium, low);
cout << "Average of the temperatures: " << ave << endl;
cout << "Number of high temperatures: " << high << endl;
cout << "Number of medium temperatures: " << medium << endl;
cout << "Number of low temperatures: " << low << endl;
//writeFile (F, C, ctr, grades);
return 0;
}
(Code from https://drive.google.com/file/d/0BxeZTCUL3Q4oZHlqWFdjMDZub0E/view?usp=sharing)

Answer 1

Without checking the whole code I can directly think of some parts of the code.
Let me start with
while (!load.eof()) {
load >> x[y];
y++;
}
Where you write more values than x[] can hold and your program will crash in that case.
Make sure to only write to your array up to the maximum allocated memory.
The problem is that !load.eof() will not do what you expect it to do as it will be read from beyond the end of the file. It will execute your loop one more time too much.
Second:
int ctr=0, high, medium, low;
float F[ctr], C[ctr], ave;
char grades[ctr];
ctr is 0 so you declare Arrays of F, c and grades with 0 elements. That's not very clever ;) You can't read or write from them.