The 1963 Constitution of Nigeria was written and rigid. This means that the constitution was a written document that provided a clear and specific framework for the governance of Nigeria. It was also rigid in the sense that it could not be easily amended or changed, requiring a more complex process than a simple majority vote. The 1963 Constitution replaced the previous 1960 Constitution and provided for a federal system of government, with powers shared between the central government and the regional governments. It also established a parliamentary system of government, with a Prime Minister as the head of government and a ceremonial President as the head of state.