Armenian is separate branch in the Indo-European family of languages. The Armenian alphabet was created in 405 A.D. It consists of 39 letters, of which 36 were created by the auther of the alphabet Mesrop Mashtots, the other 3 were added later. It was meant to suit the sound system of Armenian. These 39 letters present all the sounds of Armenian language. There is nearly one to one correspondence between the Armenian sounds and the letters that present them. The exceptions are the letters , , which represent combinations of sounds.
Source - A.V. Gevorkian "East Armenian course".