The thesis examines the role of instructions in art by developing a theory of a text machine. This machine is explored through a discussion of its rules and instructions and its codes and inscriptions. The text machine is defined independently of particular instances of its making, of specific technologies, but for the practice part of this submission text machines are simulated by computer. This occasions a discussion of the impact of one machine (the computer) upon another machine, the text machine. This became my research question. This question is posed in this form: "What is the impact of the computer on the text machine?" A complex response to this question is developed by a discussion of rules and instructions, codes and inscriptions and their interrelationships. Larger questions are also raised, such as the use of text machines in day-to-day situations.