The history of French language is divided into 6 main periods:
Gallo-Romance (5th-8th centuries)
The Vulgar Latin in Gaul has developped specific features that made it distinct from the Latin spoken in the other regions of the Roman empire. The Reichenau Glosses are a good example of its phonetics and vocabulary.
Old French (9th-13th centuries)
The dialects of Northern Gaul developed into separate language (Langue d’oil, see below) with a grammar of its own. The first written materials in it date from the Strasbourg Oaths of 842. The Old French literature flourished since the 10th century (chansons de geste etc.). French in this period was already taught in the neighboring countries (especially in Germany). In 11th-13th centuries it was the dominant language of the English administration (see more in the Romance Influences on English). It was, also, the language of the crusaders in the Levantine countries.
Middle French (14th-15th centuries)
This period was marked by changes both in the pronunciation and in the grammar. A common literary language, based on the dialect of Île de France (the region of Paris), was promoted by the writers. French was replacing Latin in the texts of the public administration in France.
Early Modern French (16th century)
The aim of the writers of this period, as is the case of the poets of La Pléiade, was to elevate the French language to the level of Latin as a medium for literary expression, In 1539 a royal decree proclaimed French official language of the public administration. Since that period the government was always involved in the development and the standardization of the language.
Classical Modern French (17th-18th century)
In this period were fixed the main grammar convention of the modern French. By then it was used as an international language throughout Europe and even in the administrative correspondence of countries as Germany. With the colonial expansion of France French spread to America (Canada, Louisiana, the Caribbean islands etc.).
Contemporary Modern French (since 19th century)
The contemporary pronunciation of the standard language was fixed in that period, namely between 1789 and 1918. French was established as an official language in the French and Belgian colonial possessions in Africa.