How cin or scanf works

[A1]

Lets i have a code like this:

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#include <iostream.h>

int main()
{
	int x;
	char s[100];

	cin>>x;
	cin>>s;
	cout<<x<<" "<<s<<endl;
	return 0;
}

And my input is:

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123nospace

The Output of this program is:

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123 nospace

Here my question is how cin or scanf() stop reading immediately before a non numeric character when it reads a number?
Does they change input pointer?
(Actually i want to implement this kind of function in java, is it possible?)

[A1]

I belive some body knows some thing about this
or any links that can help me..

[Moha]

They have a buffer and see the next character.
Also you can see the next character without extracting it from buffer.