#include <iostream>
using namespace std;

bool isSorted(int number[], int SIZE);/* You're defining a prototype here, so no variable names */

int main()
{
    cout << " Enter list: ";
    int SIZE;/* only const are ALL_CAPS */
    cin >> SIZE;
    const int A = SIZE;/* Why redefine size as A instead of just using size? */
    int number[A];

    for (int i = 0; i < SIZE; i++)
    {
        cin >> number[i];
    }

    if (isSorted)
        cout << " The list is already sorted \n" << endl;
    else
        cout << " The list is not sorted \n" << endl;

    return 0;
}

bool isSorted(int number[], int SIZE)
{
    for (int i = 0; i < SIZE; i++)
    {
        if (number[i] > number[i + 1])
            return false;
    }
 /* What if it is sorted?  Where do you return true in that case? */
}