Old Mon script

The Old Mon script was a script used to write Mon, and may also be the source script of the Burmese alphabet. 
History.
The Old Mon language might have been written in at least two scripts. The Old Mon script of Dvaravati (present-day central Thailand), derived from Grantha (Pallava), has conjecturally been dated to the 6th to 8th centuries AD.
The second Old Mon script was used in what is now Lower Burma (Lower Myanmar), and is believed to have been derived from Kadamba or Grantha. According to mainstream colonial period scholarship, the Dvaravati script was the parent of Burma Mon, which in turn was the parent of the Old Burmese script, and the Old Mon script of Haripunjaya (present-day northern Thailand). However, no archaeological evidence or any other kind of proof that the Dvaravati and Burma Mon scripts are related exists. The extant evidence shows only that Burma Mon was derived from the Old Burmese script, not Dvaravati. (The earliest evidence of the Old Burmese script is securely dated to 1035, while an 18th-century casting of an old Pagan era stone inscription points to 984. The earliest securely dated Burma Mon script is 1093 at Prome while two other "assigned" dates of Old Burma Mon are 1049 and 1086.)
However, Aung-Thwin's argument that the Burmese script provided the basis for the Mon script of Burma relies on the general thesis that Mon influence on Burmese culture is overstated. According to Aung-Thwin, the backwardness of lower Burma and the Irrawady delta as compared to upper Burma during the Pagan period, and the lack of verifiable Mon presence in lower Burma during Pagan period, implies that the Mon could not have influenced a civilization as sophisticated as Pagan. According to Stadtner's rebuttal of Aung-Thwin, these assumptions are not backed by archaeological evidence. Pottery shards from Winka, 28 km to the northwest of Thaton, bears inscriptions in Mon that have been paleographically dated to the sixth century. Furthermore, contrary to Aung-Thwin's assertion that the Mon script of Burma cannot be attributed to the script used in Dvaravati because of a four century gap between the first appearance of the former and the last appearance of the latter, Mon inscriptions from after the Dvaravati period contemporary with the Mon inscriptions at Pagan appeared where Mon inscriptions have appeared previously in the epigraphical record, such as in northern Thailand and Laos. Such a distribution, in tandem with archaeological evidence of Mon presence and inscriptions in lower Burma, suggests a contiguous Mon cultural space in lower Burma and Thailand. In addition, there are specifically Mon features in Burmese that were carried over from the earliest Mon inscriptions. For instance, the vowel letter အ has been used in Mon as a zero-consonant letter to indicate words that begin with a glottal stop. This feature was first attested in Burmese in the 12th century, and after the 15th century, became default practice for writing native words beginning with a glottal stop. In contrast to Burmese, Mon only uses the zero-consonant letter for syllables which cannot be notated by a vowel letter. Although Mon of the Dvaravati inscriptions differ from Mon inscriptions of the early second millennium, orthographical conventions connect it to the Mon of the Dvaravati inscriptions and set it apart from other scripts used in the region. Given that Burmese is first attested during the Pagan era, the continuity of orthographical conventions in Mon inscriptions, and the differences between the Pyu script and the script used to write Mon and Burmese, scholarly consensus attributes the origin of the Burmese script to Mon. The Pyu itself shows broad stylistic variations, with the Myazedi inscription showing stylistic influence from Mon and Burmese while older inscriptions from Rakhine State showing affinities with the North Indic script Siddham.
The calligraphy of modern Mon script follows that of modern Burmese. Burmese calligraphy originally followed a square format but the cursive format took hold in the 17th century when popular writing led to the wider use of palm leaves and folded paper known as "parabaiks". The script has undergone considerable modification to suit the evolving phonology of the Burmese language, but additional letters and diacritics have been added to adapt it to other languages; the Shan and Karen alphabets, for example, require additional tone markers.