The Sumerians were the first people to migrate to Mesopotamia, they created a great civilization. Beginning around 5,500 years ago, the Sumerians built cities along the rivers in Lower Mesopotamia, specialized, cooperated, and made many advances in technology. The wheel, plow, and writing (a system which we call cuneiform) are examples of their achievements.
1 In a Parliamentary System, the head of state is usually a different person than the head of government (not in every country). 2  The HOG is often vested with more official power, but holds that position for a relatively short time.
A presidential system is a system of government where a head of government is also head of state and leads an executive branch that is separate from the legislative branch.The United States, for instance, has a presidential system.The executive is elected and often titled president and is not responsible to the legislature and cannot, in normal circumstances, dismiss it.n a full-fledged presidential system, a president is chosen directly by the people or indirectly by the winning party to be the head of the executive branch. Presidential governments make no distinction between the positions of head of state and head of government, both of which are held by the president.