C :

#include<stdio.h>
void Print( int n )
{
	int i, j;
	for( i = 1; i <= n; ++i )
	{
		for( j = 1; j <= n; ++j )
			printf( "*");
		putchar( '\n' );	
	}
	return;
}
int main( int argc, char **argv )
{
	int n;
	scanf( "%d", &n );
	Print( n );
	return 0;

}

C++ :

//输出n行n列星号方阵.cpp
#include<iostream>
using  namespace  std;
int  main()
{
    int n;
    cin>>n;
    for(int j=1;j<=n;j++)
    {   
        for(int i=1;i<=n;i++)
       {
            cout<<"*"; 
       }
            cout<<endl;           
    }
}