# include <stdio.h>

int main ( )
{
  double a[2][2];
  double b[2][2];
  double det;
  int i;
  int j;
//
//  To read a double, you need to use the format "LF" for "long float".    
//
  printf ( "Enter a 2x2 matrix, row 1, then row 2:" );
  scanf ( "%lf%lf%lf%lf", &a[0][0], &a[0][1], &a[1][0], &a[1][1] );

  printf ( "\n" );
  printf ( "The matrix:\n" );
  printf ( "\n" );

  for ( i = 0; i < 2; i++ )
  {
    for ( j = 0; j < 2; j++ )
    {
      printf ( "  %8f", a[i][j] );
    }
    printf ( "\n" );
  }
//
//  Compute the determinant.
//
  det = a[0][0] * a[1][1] - a[0][1] * a[1][0];
//
//  If the determinant is zero, bail out.
//
  if ( det == 0.0 )
  {
    printf ( "The matrix does not have an inverse.\n" );
    return 1;
  }
//
//  Compute the entries of the inverse matrix using an explicit formula.
//
  b[0][0] = + a[1][1] / det;
  b[0][1] = - a[0][1] / det;
  b[1][0] = - a[1][0] / det;
  b[1][1] = + a[0][0] / det;
//
//  Print it out.
//
  printf ( "\n" );
  printf ( "Inverse matrix:\n" );
  printf ( "\n" );

  for ( i = 0; i < 2; i++ )
  {
    for ( j = 0; j < 2; j++ )
    {
      printf ( "  %8f", b[i][j] );
    }
    printf ( "\n" );
  }

  return 0;
}