|Also Known As: Old Castilian,Old Spanish Language
Old Spanish, or Old Castilian (ISO 639-3 code osp), is an early form of the Spanish language that was spoken on the Iberian Peninsula from the 10th century until roughly the beginning of the 15th century, before a consonantic readjustment gave rise to the evolution of Modern Spanish. The epic poem Cantar de Mio Cid, published around 1200, remains the best-known and most extensive work of literature in Old Spanish.
The phonological system of Old Spanish shared similarities with the modern Romance languages. Amongst the consonants, there were three pairs of sibilants, each pair consisting of one voiceless and one voiced member:
The Modern Spanish sound [x] (voiceless velar fricative), corresponding to the letter j or to g before e or i, and the Modern Spanish sound [θ] (voiceless dental fricative), written as z or as c before e or i, did not exist in Old Spanish.
The letter v was pronounced as a voiced, variously bilabial or labiodental, fricative.
The letter f represented variously a labiodental, bilabial, or glottal fricative (like the English h) that later disappeared from pronunciation, but it is now represented by an orthographic h.
In Old Spanish the perfect tenses of..... full article at Wikipedia