"Uninitialized Local Variable Used" - c++

Question

I have a call to 2 functions which find the highest and lowest grade, respectively. they return "highestGrade" and "lowestGrade" but I am confused why the error appears when I compile. This is a lab assignment and most of the code was pre-written and I was tasked with filling in the missing code. The error occurs around lines 55 and 63, and the functions I am referring to are at the end of the code.
I am new to using arrays so I am assuming I may have some for of erroneous code inside the functions "findHighest" and "findLowest". For example, the program in "findHighest" will assume the first array it runs into is the highest grade and will compare the remaining arrays to it until it finds one that is higher. If it is, it will then assign that array to "highestGrade".
float findAverage(const GradeType, int);
int findHighest(const GradeType, int);
int findLowest(const GradeType, int);
int main()
{
GradeType grades;
int numberOfGrades;
int pos;
float avgOfGrades;
int highestGrade;
int lowestGrade;
// 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];
int i = 1;
while (grades[pos] != -99)
{
// read in more grades
pos = i;
cout << "Please input a grade from 1 to 100, (or -99 to stop)" << endl;
cin >> grades[pos];
}
numberOfGrades = pos; // Fill blank with appropriate identifier
// call to the function to find average
findAverage(grades, numberOfGrades);
avgOfGrades = findAverage(grades, numberOfGrades);
cout << endl << "The average of all the grades is " << avgOfGrades << endl;
// Fill in the call to the function that calculates highest grade
findHighest(grades, highestGrade);
highestGrade = findHighest(grades, highestGrade);
cout << endl << "The highest grade is " << highestGrade << endl;
// Fill in the call to the function that calculates lowest grade
findLowest(grades, lowestGrade);
// Fill in code to write the lowest to the screen
lowestGrade = findLowest(grades, lowestGrade);
cout << endl << "The lowest grade is " << lowestGrade << endl;
return 0;
}
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
}
int findHighest(const GradeType array, int size)
{
// Fill in the code for this function
float highestGrade = array[0];
for (int i = 0; i < size; i++)
{
if (array[i] > highestGrade)
highestGrade = array[i];
}
return highestGrade;
}
int findLowest(const GradeType array, int size)
{
// Fill in the code for this function
float lowestGrade = array[0];
for (int i = 1; i < size; i++)
{
if (array[i] < lowestGrade)
lowestGrade = array[i];
}
return lowestGrade;
}
The program is unable to output the highest and lowest grade due to the error.

Answer 1

findLowest(grades, lowestGrade);
You are using lowestGrade before initializing it.
int lowestGrade;
should be
int lowestGrade = 0; // or to anything that has meaning for your app.
And of course, as better C++, declare it just before you need it, not at the top of the function.
Same thing for the other variables.
All of this of course if the logic is correct. Why do you pass the lowest/higest grade as a size parameter in the functions?