Help with a pretty big C++ assignment

Hello, i was searching for some forums to get some help with an assignment i am completely lost with and thought somebody here could help. Have a quiz similiar to this problem next week so any help would be real nice.

Code:

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//  Edit the code in this file so that it does the following:
//
//    In the main function:
//    + Display the menu.
//    + Input a character from the user representing a menu choice.
//    + Use a switch statement to selectively execute code satisfying the
//    + user's choice.
//    + Give the user a chance to enter another choice.
//    + If the user enters '0', 'q' or 'Q' for a choice the program should
//    + exit.
//
//    *NOTE:
//      -- Code that needs to be added or corrected is in RED
//      -- Call all functions using arguments indicated by the function
//          prototypes and definitions.  Do not place code in main() that
//          should be in another function definition.   


// This section of the handout serves to illustrate certain aspects of
// C++.  You should study this section.  Many of the functions contain
// code that is not correct (dummy code).  This code should be
// corrected.  Compile and run the code.  Some of what you learn in this
// section will apply to the assignment, which is described at the end
// of this handout.  You will use the functions developed in this
// section in your assignment.  This section of the handout will serve
// as the basis of your assignment.  You may copy this section to your
// assignment source file.


//  Topics covered:
//  reference parameters
//  passing array to function as a pointer
//  pointer variables
//  call by reference with pointer arguments
//  call by reference with reference arguments
//  switch statement
//  character mode menu
//  dynamic memory allocation for array
//  pointer arithmetic


#include <cstdlib>
#include <iostream>
#include <iomanip>
#include <ctime>
using namespace std;


// For function prototypes we only need specify the data types to be
// passed to the functions.  If any parameter names are mentioned, they
// are ignored by the compiler.
void fill(int ax[], int nx);
void display(int* pax, int nx);
void max_min (int* pax, int nx, int& maxx, int& minx);
long sort(int* pax, int nx);
long sum(int* pax, int nx);
long search(int ax[], int nx, int snumx, int& posx);
void menu();
float avg(int* , int nx);  // only included data type for the first item
int div3(int* , int nx);
int mode (int* , int );    // only data types for both items


int main(void)
{
    int const n=25;
    int* a = new int[n];  // Dynamically allocate storage to array at run time.
    srand(time(0));      // Randomizer uses current system time for randomize seed.
    char choice;          // Declaration of choice variable.
    int snum, pos = -1;

 
    do
    {
        // char choice;    // why not declare choice here?

        menu();            // display menu

        cin >> choice;    // get menu choice from user

        switch(choice)
        {
        case '1':
            fill(a,n);
            break;

        case '2':
            cout <<'\n'<< "Displaying array a..." << endl;
            display(a,n);
            break;

        case '3':
            cout <<'\n'<< "The number of comparisons needed for "
                << "sorting the array is.. " << sort(a,n) << endl;
            // sort(a,n) returns the number of comparisons
            // needed to sort a[0]..a[n-1]
            break;

        case '4':
            int max, min;
            max_min(a, n, max, min);
            cout <<'\n'<< "The max number is.. "<< max;
            cout <<'\n'<< "The mimumum number is.. "<< min << endl;
            break;

        case '5':
            // ask user for search number
            cout << endl << "Please enter a search integer: ";
            cin >> snum;            // store search integer in snum
            search(a,n,snum, pos);  // return value of search should be stored
                                    // for later use.

            if (pos == -1)
            {
                // Tell the user snum was not found.
                // Indicate the number of comparisons needed
                // to determine that snum was NOT in the array a[0]..a[n-1].
                // This number (the # of comparisons) is the
                // return value from the search function (see implementation).
            }
            else
            {
                // snum was found in the array a[0]..a[n-1].
                // Tell the user the number of comparisons needed
                // and the position in the array (pos) where snum was found.
                // i.e.  a[pos] = snum
            }

            break;

 
        case '6':
            cout << "\n The sum is.. "
                << sum(a,n) << endl;
            break;

        case '7':
            // call divisible by three algorithm
            cout << "\n There are "
                << div3(a,n) << " numbers in the array"
                <<  " divisible by 3." << endl;
            break;

        case '8':
            // call your code for avg
            cout << "\n The AVERAGE of the.. " << n << " numbers is.. "
                << avg(a,n) << endl;
            break;

        case '9':
            // call your code for mode
            cout << "\n The MODE of the.. " << n << " numbers is.. "
                << mode(a,n) << endl;
            break;

        case '0': case 'Q': case 'q':                // all three quit
            cout <<'\n'<< "Thanks...."<< endl << endl << "goodbye." << endl;
            break;

        default:

            cout <<'\n'<< "Wrong Key" << endl;
            break;
        }    // end of switch

    } while (choice != '0'|| choice!='Q' || choice!='q');
            // ERROR IN LOGIC, BEWARE !!!!!!!
            // toupper() or tolower() may be used to make the condition a
            // little simpler.  These functions may be found in ctype.h

    return 0;
}  // End of main()


void fill(int ax[], int nx)
{
    for (int j=0; j<nx; j++)
    {
        ax[j]=1+ rand()%10; // generates random numbers between 1 and 10
    }
}


 
void display(int* pax, int nx)
{
    int r, j;

    for (j=0; j<nx; j++)
    {
        cout << setw(7) << *(pax+j); // pointer arithmetic

        // What will the next two statements do?
        r = (j+1) % 10;      // zero when (j+1) is multiple of ten
        if (!r)
            cout << endl;    // if r==0 then
                              // !r is not zero (i.e. it's true)
    }
    cout << endl;
}


long sum(int* pax, int nx)
{ 
    long s = *pax;    // Initialize s to the first element of the array
    s += *(pax+1);    // Add to s *(pax+2); the second element
                      // Correct this function.  Write the code to sum
                      // the number of integers (nx) in the array pointed
                      // to by pax.  USE POINTER ARITHMETIC TO ADDRESS THE
                      // ARRAY.
    return s;
}

long sort(int bx[], int nx)
{
    long cnt=0;

    // Code goes here for sorting the array.
    // cnt should keep track of the number of
    // comparisons necessary for sorting.

    return cnt;      // number of comparisons
}

void menu()
{
    cout << endl;
    cout << " 1.  Fill array" << endl;
    cout << " 2.  Display array"<< endl;;
    cout << " 3.  Sort array" << endl;
    cout << " 4.  Largest and smallest" <<endl;
    cout << " 5.  Search routine" << endl;
    cout << " 6.  Sum the array" << endl;
    cout << " 7.  Integers divisible by 3" << endl;
    cout << " 8.  Average" << endl;
    cout << " 9.  Mode value" << endl;
    cout << " 0.  Quit" << endl;
    cout << " Choice ----> ";
}


void max_min (int* ax, int nx, int& maxx, int& minx)
{
    // Return the max (maxx) and min (minx) of the array as references.
}

long search(int* ax, int nx, int snumx, int& posx)
{
    long cmp=0;

    // Search for snumx in the array ax of size nx.
    // Return the number of comparisons needed to find or not find
    // the search integer through the function name.  If you find snumx
    // in the array, then store the value of the position in the reference
    // variable posx.
    //
    // EX:
    // If ax points to { 12 4 55 6 } and you were searching for 4
    // then posx should be assigned the value 1 since 4
    // is in the 1st position in the array (12 is in the 0th position)

    return cmp;        // number of comparisons
}

float avg(int* ax, int nx)
{ 
  float f;
    // Compute the average of the numbers in the array.
    // CALL THE SUM FUNCTION THEN DIVIDE by NX (the size of the array).

    return f;
}

int div3(int* ax, int nx)
{
    int d3 = 0;
    // Use the modulus operator ( % ) to determine
    // how many integers there are in the array that are
    // divisible by three.

    // EX:
    // If ax points to { 1 2 4 5 5 6 } then there is 1 integer divisible
    // by three in the array.

    return d3;        // d3 is assigned the value 0. This is wrong.
}

int mode(int* ax, int nx)
{
    int most = 0;

    // Determine which number in the array appears most often (this is the mode).
    // In case of ties return any of the mode values.

    // EX:
    // if ax = { 1 4 5 5 } then the mode is 5 (return 5)
    // if ax = { 1 1 5 5 } then the mode is 5 and 1 (bimodal)  (return 5 or 1)

    return most;       
}

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which part are you having trouble with? you should have read the rules, we cannot write the code for you, nor should you ask such general questions. try to do it first, give us some code that doesn't work, then we can help you.