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 presidential system, the legislature and the executive do not have to be aligned and often work against each other. 2  Policy implementation can be much slower and more moderated, at least in the US system.
In a Presidential System, the President fulfills both roles (Head of State and Head of Government). In a Parliamentary System, theoretically, an election can be called at any time but there is usually a maximum time that a legislature can sit (4 or 5 years).nd in the Presidential system the Head of the Government and the Head of the Country is same person. For example in United State America the Head of the Government and the Head of the Government is U.S.A's President.