Cal is a robot whose master is an author. Set in the Age of Robots, the word processor is called the Writer. Cal, under the influence of his master, decides to learn to write. His master outfits his mind with a dictionary and gives him advice and a few of his own books to read, as well as a grammatical dictionary. Cal tries to write mystery like his master, but is hampered by the Three Laws of Robotics; a robot's aversion to harming a human makes Cal cut out all violence, making the mystery rather inane. Instead, his master decides to give him the knack of recognizing humor. Cal writes a very good story on this new topic: so good, in fact, that his master is afraid of being put in the shade and 'playing second dog to a robot'. He orders the technician to remove Cal's abilities. Cal, hearing this, decides to kill his master, in defiance of the First Law, because apparently his new abilities take precedence: "I want to be a writer."
The humorous story written by Cal is in fact one of Asimov's Azazel stories.