draw an empty square of asterisks

Hi everyone, im new to C and I'm stuck doing an exercise that asks me to draw an empty square of " * " using "while" and where n = side (side must be >=1 and <= 20) I succeeded to make a square of asterisks like this:

Code:

n = 6
******
******
******
******
******
******

now i need to do the same thing but the box needs to be empty:

Code:

n = 6
******
*    *
*    *
*    *
*    *
******

This is the code i wrote for the first exercise:

Code:

#include <stdio.h>
int main()
{
	int n, i, j;
		
	printf("Insert a number between 1 and 20:\n");
	scanf("%d", &n);


			
	if ((n >= 1)&&(n <=20))
	{
			i = 0;
			while( i<n )
			{
				i++;
 				   j = 0;
					while( j<n )
					{
						printf("* ") ;
						j++;
					}
				printf("\n");			
			}
	}
		else
			printf("the square's side must be between 1 and 20.\n");

return 0;
}

Any help would be appreciate, I know this should be easy to do but im still a beginner..

Instead of while( j < n) print asterisks, how about

while (j < n)
if (j == 1)
print asterisk

Now combine the left and right border (which are the only places you need to print up an asterisk, into one if statement:

if( j == left border || j == right border)
print asterisk

same like my assignment lastweek.. hahaha..
if you look the combination

Code:

if N=5
  1 2 3 4 5
1* * * * *   
2*        *
3*        *
4*        *
5* * * * *

the number is up to you(when you start, 0 or 1 at for)
row one, row five, column 1, and column 5, else print space...
hehehe.. hope you get the way...

I solved it:

Code:

#include <stdio.h>
int main()

{
	int n, i, j, f;
		
	printf("Insert a number (1-20):\n");
	scanf("%d", &n);


			
	if ((n >= 1)&&(n <=20))
	{

		i = 0;
		while(i < n)
		{
			i++;
				j = 0;
				while(j <= n)
				{		

					if (((j > 1)&&(j < n))&&((i > 1)&&(i < n))) 
					{
						printf("  "); 
					}
					else if((j !=0 )&&(i!=0))
					{
						printf("* ");
					}

					j++;
				}
			printf("\n");			

		}
	}
	else
	printf("the number must be between 1 and 20.\n");

return 0;
}

Thanks for the help ;D