More Array code problems

In this program I'm trying to use arrays to keep track of the (x,y,z) coordinates of a given number of projectiles, starting from (0,0,0). I hope to use this as the basis for a collision system for a game. The only clear error is the x value has an incorrect value after the program executes. I think there is also problems with the looping, but I can probably fix that myself. Here's the code.

Code:

Code:

#include <iostream>

using std::cout;
using std::cin;
using std::endl;


int a,n,x;
int forcex, forcey, forcez;

int main()
{
	
	cout<<"How many projectiles are fired?:";
	cin>>a;
	cout<<"What is the vector acceleration?"<<endl;
	cout<<"x:";
	cin>>forcex;
	cout<<"y:";
	cin>>forcey;
	cout<<"z:";
	cin>>forcez;
	cout<<"There is force at ("<<forcex<<","<<forcey<<","<<forcez<<")"<<endl<<endl;

	int posx[]={0}, posy[]={0}, posz[]={0};
	
	for(n=0;n<a;n++)
	{
		posx[n] = posx[n]+forcex;
		posy[n] = posy[n]+forcey;
		posz[n] = posz[n]+forcez;
	
		for(x=1;x<n+2;x++)
		{			
			cout<<"The position of particle "<< n+1 <<" is:"<<endl;
			cout<<"("<<posx[x]<<","<<posy[x]<<","<<posz[x]<<")"<<endl<<endl;
		}
	}

	return 0;
}

When inputting all variables as 1, the output coordinate is: (1245120,1,1). Assuming that I'm not changing the values of the posx[] array, I dont know what is causing this error. Please help!

It looks like you want something like

int posx[MAX_PROJECTILES] = { 0 };
int posy[MAX_PROJECTILES] = { 0 };
int posz[MAX_PROJECTILES] = { 0 };

Instead of the array with only one element.

I'm also not sure what you're inner loop with indice x also needs to be fixed. Also you don't ever want variables for indices global, because it makes your program hard to understand.