In 2151, the Enterprise NX-01 explored the pre-warp civilization. The accoustic relay picked up "dozens of languages" from the planet, Communications officerHoshi Sato joked that she could spend ten years studying the planet. She noted that their name for their own species was "Akaali", but setting up a translation matrix for which language they would need depended on the landing site they selected. (ENT: "Civilization")
From examples of written language seen in the episode, it would appear that it could be written both horizontally and vertically.