matrix magic , can you explaind this code pliz

#include<stdio.h>
int main()
{
int i, j = 1, l, n;
int mm[50][50], x, y, z;
int c = 0;
label:
printf(“Enter the Order of Magic Matrix(Odd) : “);
scanf(“%d”, &n);
printf(“\n”);
if (n % 2 == 0)
{
printf(“Enter Odd Numbers Only\n\n”);
goto label;
}
//find the middle column
l = (n + 1) / 2;
//set all the elements to be used to 0
for (x = 1; x <= n; x++)
{
for (y = 1; y <= n; y++)
{
mm[x][y] = NULL;
}
}
for (i = 1; i <= (n * n); i++)
{
if (mm[j][l] == NULL)
{
mm[j][l] = i;
}
else
{
j = j + 2;
l–;
if (j == n + 2)
j = 2;
if (l == 0)
l = n;
if (j == 0)
j = n;
if (l == n + 1)
l = 1;
mm[j][l] = i;
}
j–;
l++;
if (j == 0)
j = n;
if (l == n + 1)
l = 1;
}
for (x = 1; x <= n; x++)
{
for (y = 1; y <= n; y++)
{
z = mm[x][y];
while (z > 0)
{
z = z / 10;
c++;
}
if (c == 1)
printf(” 0%d”, mm[x][y]);
else
printf(” %d”, mm[x][y]);
if (y % n == 0)
printf(“\n\n”);
c = 0;
}
}
return 0;
}