How to use new to allocate space?

[misslyss]

I have no idea how to use new or what it means. I would appreciate it if someone can explain it to me in an easy to understand way since I am a beginner.

[ne555]

int *foo = new int [x];

> I just have no idea (...) what it means
¿what?

[MiiNiPaa]

http://www.cplusplus.com/doc/tutorial/dynamic/

[misslyss]

thanks guys!! :)

[Pindrought]

One way to use new is like using a dynamic array.

So for example, if we have

int MyArray[100];

Then we have an array of size 100 that can never be resized. Using new, we could get this effect by doing

int * MyArray = new int[100];

However, in this example we could choose the size of our array by changing the number in the brackets. That being said, we could do something like

#include <iostream>
using namespace std;
int main()
{
	int ArraySize;
	cout << "Enter Array Size:";
	cin >> ArraySize;
	int * MyArray = new int[ArraySize]; //This would create an array of size ArraySize
	for (int i = 0; i < ArraySize; i++)
	{
		cout << "Enter an integer:";
		cin >> MyArray[i];
	}
	delete[] MyArray;
	return 0;
}

If you notice, after I was done using MyArray, I called delete[] MyArray;

Every time you use new, you need to use delete when you're done with that memory. If you don't, then you have memory leaks.

[MiiNiPaa]

If you notice, after I was done using MyArray, I called delete MyArray;

And you just got undefined behavior in your program.

You should never ever use delete for anything allocated with new[], and likewise, never use delete[] for something allocated with new.
Eacch new should be paired with delete and new[] with delete[]

[Pindrought]

Was a typo, but MiiniPaa is correct you should use delete[] with new[] and delete with new.