Constitutions have been classified into different categories. They may be written or unwritten.
The constitutions of most countries are written ones. In a written constitution the fundamental laws of the state are stated. As a result, the constitution is largely free from ambiguity. The government, elected representatives and people clearly know what they should do what they can do, and what they cannot do.
A written constitution is a conscious act. It is the product of a deliberate process. It is framed by a committee of statesmen, lawyers, scholars and others having good knowledge of the working of a political system.
The American constitution, adopted in 1787, happens to be the first written constitution in the world. The longest written constitution in the world is the Indian constitution promulgated on 26 January 1950.
There are, however, a small number of states which do not have written constitutions. Besides some dictatorships which do not want, for obvious reasons, to have written constitutions, three liberal democracies like Israel, New Zealand and Britain do not have written constitutions. The latter are governed by unwritten constitutions. Britain is the classic case of being governed by an unwritten constitution.
An unwritten constitution is not the product of a deliberate act. It grows over time. It is the product of long evolution of a number of customs, conventions and traditions.
It may, however, be emphasized that no constitution is either fully written or fully unwritten. A written constitution respects some conventions while a so-called unwritten constitution also contains some written laws.
The American constitution provides that the President of America is elected indirectly, but, in practice, he is elected directly. His election is governed by a convention, not by the written rule of the constitution. On the other hand, several important constitutional documents like the Magna Carta of 1215.’, the Petition of Rights of 1628, the Habbeas Corpus Act of 1679, the Parliamentary Act of 1911 and the Crown Proceeding Act of 1947 govern the functioning of the British political system.