Final answer:
A legal system based on written codes is known as civil law, which is distinct from common law that relies on judicial decisions and precedents.
Step-by-step explanation:
The legal system that is based on written codes, such as laws, rules, or regulations, is known as civil law. This system contrasts with common law, which is primarily developed by judges through decisions in courts and relies heavily on precedents. Civil law provides comprehensive laws that guide judges in application, leaving less room for interpretation than in a common law system.
In civil law, the focus is on adhering to the detailed codes written by the legislative body. An example of a civil law system can be found in countries like France, where the legal structure is based on written codes rather than judicial rulings.