Instruments similar to what we know as the guitar have been popular for at least 5,000 years. The guitar appears to be derived from earlier instruments known in ancient central Asia as the cithara. Instruments very similar to the guitar appear in ancient carvings and statues recovered from the old Iranian capital of Susa.
During the MiddleAges, guitars with three, four, and five strings existed. The Guitarra Latina had curved sides and is thought to have come to Spain from elsewhere in Europe. The Guitarra Morisca, brought to Spain by the Moors, had an oval soundbox and many sound holes on its soundboard. By the fifteenth century, four double-string guitars, similar to lutes, became popular, and by the sixteenth century, a fifthdouble-string had been added. During this time, composers wrote mostly in tablature notation. Italy was the center of guitar world during the 17th century, and the Spanish school of guitar making only began to flourish late in the 18th century after the addition of the sixth string. During the 19th century, improved communication and transportation enabled performers to travel widely and the guitarbecame a widely known instrument. Guitar music became especially popular in Spain and Antonio de Torres developed the Spanish guitar in its modern form, with a broadened body, increased waist curve, thinned belly, improved internal bracing, single string courses replacing double courses, and a machined head replacing wooden tuning pegs.
THE RENAISSANCE GUITAR
The gittern, Englishfor Renaissance guitar, is a musical instrument resembling a small lute or guitar. It is related to but is not a citole, another medieval instrument. The gittern was carved from a single piece of wood with a curved ("sickle-shaped") pegbox. An example has survived from around 1450.
The written history of the classical guitar can be traced back to the early sixteenth century withthe development of the vihuela in Spain. While the lute was then becoming popular in other parts of Europe, the Spaniards did not take to it well because of its association with the Moors . They turned instead to the four string guitarra, adding two more strings to give it more range and complexity. In its most developed form, the vihuela was a guitar-like instrument with six double strings made ofgut, tuned like a modern classical guitar with the exception of the third string, which was tuned half a step lower.
"GUITAR DURING THE CLASSICAL MUSIC ERA"
The earliest extant six string guitar was built in 1779 by Gaetano Vinaccia (1759 - after 1831) in Naples, Italy. The Vinaccia family of luthiers is known for developing the mandolin. This guitar has been examined and does not showtell-tale signs of modifications from a double-course guitar.  The authenticity of guitars allegedly produced before the 1790s is often in question. This also corresponds to when Moretti's 6-string method appeared, in 1792.
CONTEMPORARY CLASSICAL GUITAR
Contemporary concert guitars occasionally follow the Smallman design which replaces the fan braces with a much lighter balsa brace attached tothe back of the sound board with carbon fiber. The balsa brace has a honeycomb pattern and allows the (now much thinner) sound board to support more vibrational modes. This leads to greater volume and longer sustain.
MULTI-STRING CLASSICAL GUITAR
A multi-string classical guitar is a classical guitar with more than 6 strings, usually between 7 and 10.
MODERN 10-STRING GUITAR
The Modern/Yepes10-string guitar adds four strings (resonators) tuned in such a way that they (along with the other three bass strings) can resonate in unison with any of the 12 chromatic notes that can occur on the higher strings; the idea behind this being an attempt at enhancing and balancing sonority.
ANTONIO DE TORRES JURADO
(June 13, 1817 – November 19, 1892) was a Spanish guitarist and guitar maker....