Problem while reading and printing an array

I'm a newbie and started to code couple of days ago. So today started with array and have some doubts. I'm reading a array by taking input from user and displaying it everything s running fine but on ouput screen I'm having a garbage value and dont know why. Please help me.

#include <iostream>
using namespace std;

int main(){
	int number;
	cout<<"Enter a array_size"<<endl;
	cin>>number;

	//Reading and printing array
	int array[number];
	int i=1;
	while(i<=number){
		cin>>array[i];
		i++;
	}
	//printing array
	int j=0;
	while(j<=number){
		cout<<array[j]<<endl;
		j++;
	}
}

Expected output: Reading from user: 3

1
2
3
//displaying
1
2
3

Actual result: Reading from user: 3

1
2
3
16
1
2
3

Why 16 is showing?

As mentioned in the comments, c++ does not support VLA (variable length arrays) - see here: https://stackoverflow.com/questions/1887097/why-arent-variable-length-arrays-part-of-the-c-standard.

It was also already mentioned that array indices start at 0, not 1 (https://stackoverflow.com/questions/2289548/array-indexing-starting-at-a-number-not-0).

You can avoid these issues using std::vector and ranged-based loops (the latter is available since c++11).

Code example for you case:

#include <iostream>
#include <vector>

int main()
{
    int number;
    std::cout << "Enter a array_size" << std::endl;
    std::cin >> number;

    // Read:
    std::vector<int> array(number);
    for (auto& elem : array)
    {
        std::cin >> elem;
    }

    // Print:
    for (auto const & elem : array)
    {
        std::cout << elem << std::endl;
    }
}

Note that auto elem : array (without &) would not have worked because auto by itself would not infer a reference and instead copy the element.

A side note: better to avoid using namespace std - see: https://stackoverflow.com/questions/1452721/why-is-using-namespace-std-considered-bad-practice.

There are 2 problems with your code.

First int array[number]; is not standard c++ as number is not a constant expression.

Second, array indices start as 0 instead of at 1 in c++.

There are also many other posts describing these problems.

Array index always start at 0

Why accessing out of bound array does not give any error

The array should always start at index 0. Update your starting index and the conditions.

//Reading and printing array
int array[number];  
int i=0; // should start with zero.
while(i<number){  // should be less than only since you start with zero.
    cin>>array[i];
    
    i++;

}
//printing array
int j=0;
while(j<number){   // should be less than only since you start with zero.
    cout<<array[j]<<endl;
    j++;
}

Array indexes start at 0, not at 1.

Corrected code:

  //Reading and printing array
  int array[number];
  int i = 0;
  while (i < number) {
    cin >> array[i];
    i++;
  }

  //printing array
  int j = 0;
  while (j < number) {
    cout << array[j] << endl;
    j++;
  }

It's more idiomatic to use a for loop here:

  //Reading and printing array
  int array[number];

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

  //printing array
  for (int i = 0; i < number; i++) {
    cout << array[j] << endl;
  }