I am working on a program and im trying to figure out the logic and it is not making any sense?

I can not figure out how to find the highest and lowest of the array in a function

// This program will read in a group of test scores( positive integers from 1 to 100)

// from the keyboard and then calculates and outputs the average score

// as well as the highest and lowest score. There will be a maximum of 100 scores.

// Meredith Martin

#include <iostream>

using namespace std;

typedef int GradeType[100]; // declares a new data type:

// an integer array of 100 elements

float findAverage (const GradeType, int); // finds average of all grades

int findHighest (const GradeType, int); // finds highest of all grades

int findLowest (const GradeType, int); // finds lowest of all grades

int main()

{

GradeType grades; // the array holding the grades.

int numberOfGrades; // the number of grades read.

int pos; // index to the array.

float avgOfGrades; // contains the average of the grades.

int highestGrade; // contains the highest grade.

int lowestGrade; // contains the lowest grade.

// Read in the values into the array

pos = 0;

cout << "Please input a grade from 1 to 100, (or -99 to stop)" << endl;

cin >> grades[pos];

while (grades[pos] != -99)

{

pos++; //changes array number

cout << "Please input a grade from 1 to 100, (or -99 to stop)" << endl;

cin >> grades[pos];

}

numberOfGrades = pos - 1; // Fill blank with appropriate identifier

// call to the function to find average

avgOfGrades = findAverage(grades, numberOfGrades);

cout << endl << "The average of all the grades is " << avgOfGrades << endl;

highestGrade = findHighest(grades, numberOfGrades);

cout << endl << "The highest grade is " << highestGrade << endl;

lowestGrade = findLowest(grades, numberOfGrades);

cout << endl << "The lowest grade is " << lowestGrade << endl;

system("PAUSE");

return 0;

}

//****************************************************************************

// findAverage

//

// task: This function receives an array of integers and its size.

// It finds and returns the average of the numbers in the array

// data in: array of floating point numbers

// data returned: avarage of the numbers in the array

//

//****************************************************************************

float findAverage (const GradeType array, int size)

{

float sum = 0; // holds the sum of all the numbers

for (int pos = 0; pos < size; pos++)

sum = sum + array[pos];

return (sum / size); //returns the average

}

//****************************************************************************

// findHighest

//

// task: This function receives an array of integers and its size.

// It finds and returns the highest value of the numbers in

// the array

// data in: array of floating point numbers

// data returned: highest value of the numbers in the array

//

//****************************************************************************

int findHighest (const GradeType array, int size)

{

float highest = 0;

for(int pos = 0; pos < size; pos++)

{

if (array[pos] >= highest)

highest = array[pos];

}

}

//****************************************************************************

// findLowest

//

// task: This function receives an array of integers and its size.

// It finds and returns the lowest value of the numbers in

// the array

// data in: array of floating point numbers

// data returned: lowest value of the numbers in the array

//

//****************************************************************************

int findLowest (const GradeType array, int size)

{

float lowest = -1;

for(int pos = 0; pos < size; pos++)

{

if (array[pos] <= lowest)

lowest = array[pos];

}

}