Thread: help using push_back

I need help using the push_back operation. See code.

Code:

#include <iostream>
#include <iomanip>
#include <cstdlib>
#include <ctime>
#include <vector>

using namespace std;

double FillVec (vector <int> &);
void PrintVec (vector <int>);
double Average (vector <int>);
int FindLargest (vector <int>);
void Exchange (vector <int> &, int);

int main (void)
{
	vector <int> Vec1 (100);
	vector <char> CharVec [26];
	float Ary1 [10];
	int IndexOfLargest, TheNum = 0;
	
	srand (time(NULL));

	FillVec(Vec1);

	cout << "The average is " << setiosflags(ios::fixed) << setprecision(2) << 
		Average (Vec1) << endl << endl;
	
	PrintVec (Vec1);

	FindLargest (Vec1);

	cout << "The largest element is " << setiosflags(ios::fixed) << setprecision(2) <<
		FindLargest(Vec1) << endl << endl;

	Exchange (Vec1, IndexOfLargest);

	PrintVec(Vec1);

	return 0;
}
double FillVec (vector <int> & ivec)
{
	int Total = 0;
	int Size;

	vector <int> MyVec (100);
	
	if (ivec.size() != 0)
	{
		MyVec = ivec;
		Size = ivec.size();
	}
	else
		Size = 100;

	for (int i = 0; i < Size; i++)
	{
		MyVec[i] = rand() % 199 - 99;
		Total += MyVec[i];
	}

	ivec = MyVec;

	return (double(Total) / ivec.size());

}
void PrintVec (vector <int> ivec)
{
	for (int index = 0; index < ivec.size(); index++)
	{
		cout << setw(5) << ivec[index];

		if (index % 10 == 9)
			cout << endl;
	}

	cout << endl;
}
double Average (vector <int> ivec)
{
	int sum = 0;
	int Size = ivec.size();

	for (int index = 0; index < Size; index++)
		sum += ivec [index];

	return (double (sum) / Size);
}
int FindLargest (vector <int> ivec)
{
	
	int maxIndex = 0;

	for (int index = 1; index < 100; index++)
		if(ivec[maxIndex] < ivec[index])
			maxIndex = index;

		return ivec[maxIndex];
}
void Exchange (vector <int> & ivec, int i)
{
	
	ivec.push_back(100);

	for (i = 0; i < 100; i++)
	ivec[i];
	
}

After finding the largest element of Vec1 and printing it out. Exchange is supposed to exchange the largest element of Vec1 with the last element of the vector. Am I using push_back correctly? I read through the section in my book about push_back, but I'm still unsure. My output just puts the number 100 at the end of the vector.
Thank You,
Kristina