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diff --git a/gr-howto-write-a-block/lib/howto_square2_ff.cc b/gr-howto-write-a-block/lib/howto_square2_ff.cc
new file mode 100644
index 000000000..e86db93dd
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+++ b/gr-howto-write-a-block/lib/howto_square2_ff.cc
@@ -0,0 +1,92 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2004 Free Software Foundation, Inc.
+ * 
+ * This file is part of GNU Radio
+ * 
+ * GNU Radio is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3, or (at your option)
+ * any later version.
+ * 
+ * GNU Radio is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with GNU Radio; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+/*
+ * config.h is generated by configure.  It contains the results
+ * of probing for features, options etc.  It should be the first
+ * file included in your .cc file.
+ */
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <howto_square2_ff.h>
+#include <gr_io_signature.h>
+
+/*
+ * Create a new instance of howto_square2_ff and return
+ * a boost shared_ptr.  This is effectively the public constructor.
+ */
+howto_square2_ff_sptr 
+howto_make_square2_ff ()
+{
+  return howto_square2_ff_sptr (new howto_square2_ff ());
+}
+
+/*
+ * Specify constraints on number of input and output streams.
+ * This info is used to construct the input and output signatures
+ * (2nd & 3rd args to gr_block's constructor).  The input and
+ * output signatures are used by the runtime system to
+ * check that a valid number and type of inputs and outputs
+ * are connected to this block.  In this case, we accept
+ * only 1 input and 1 output.
+ */
+static const int MIN_IN = 1;	// mininum number of input streams
+static const int MAX_IN = 1;	// maximum number of input streams
+static const int MIN_OUT = 1;	// minimum number of output streams
+static const int MAX_OUT = 1;	// maximum number of output streams
+
+/*
+ * The private constructor
+ */
+howto_square2_ff::howto_square2_ff ()
+  : gr_sync_block ("square2_ff",
+		   gr_make_io_signature (MIN_IN, MAX_IN, sizeof (float)),
+		   gr_make_io_signature (MIN_OUT, MAX_OUT, sizeof (float)))
+{
+  // nothing else required in this example
+}
+
+/*
+ * Our virtual destructor.
+ */
+howto_square2_ff::~howto_square2_ff ()
+{
+  // nothing else required in this example
+}
+
+int 
+howto_square2_ff::work (int noutput_items,
+			gr_vector_const_void_star &input_items,
+			gr_vector_void_star &output_items)
+{
+  const float *in = (const float *) input_items[0];
+  float *out = (float *) output_items[0];
+
+  for (int i = 0; i < noutput_items; i++){
+    out[i] = in[i] * in[i];
+  }
+
+  // Tell runtime system how many output items we produced.
+  return noutput_items;
+}