David Easton's system theory is a way to understand various political systems and their system of steps based on the idea that all political systems have precise boundaries yet are fluid in their activity. Easton's system was created in 1953 and is a continual system.
The process starts with the inputs into the government, which are the demands and the supports. Then, there is a conversion that takes place, which is internal feedback within the government, and the outputs appear, which are rewards and deprivations. From here, the government will listen to external feedback and other systems before returning once again to the inputs of demands and supports.
Easton's system theory can be used with any nation in the world. An example of his system theory in work would be when disgruntled voters in a nation decide to turn to violence in order to get their voice out. This is a demand. The government officials talk among themselves and gather internal feedback. Then this demand is converted into an output with a reward such as services and opportunities as well as deprivations such as taxes and imprisonment. Easton believed that the input was necessary because the government needs to generate internal feedback and then support for that internal feedback in order to create laws and run the country.