The first program that you learn to write in any computer language is Hello world. We maintain the convention in this book and start with the Hello world program. The code that we used in the preceding section to validate our TensorFlow installation is as follows:

import tensorflow as tf
message = tf.constant('Welcome to the exciting world of Deep Neural Networks!')
 with tf.Session() as sess:
     print(sess.run(message).decode()) 

Let's go in depth into this simple code.