For instance, programming languages and CPU instruction sets are examples of formal rule systems that access and modify data. If the rules can be used to simulate Turing's hypothetical computing machine, the rules are said to be "Turing complete." A Turing-complete system can be proven mathematically to be capable of performing any possible calculation or computer program.
- Many procedural programming languages, including C and Pascal
- Most object-oriented programming languages, such as Java and C++
- Logic programming languages, such as Prolog
- Many finite automata systems, such as Conway's Game of Life