Nepal Script is the script which can be taken as Nepal's original script on the way of script development. Ashokan Brahmi Script is the oldest script found in SAARC countries. It is also well known as Ashokan Script as king Ashoka spread this script in many places. Ashokan inscription in the Brahmi Script of 255 B.C. in pillar of Niglihawa of Kapilbastu district is the oldest one found in Nepal which roughly translates as-"king Piyadasi beloved of the gods, after 14 years of his coronation enlarged for the second time the stupa of Buddha Kanaka Muni, & after 20 years of his coronation he came himself & worshipped (&) he caused (this) stone pillar to be erected."
Gupta Script was developed in early Lichhivi period. It was in use from 4th to 7th century. Gupta Script and Kutila script are now named Pro Lichhivi script and Post Lichhivi script as decided by HMG, Archeology & culture dept. Different forms of are seen in different places such as in Devanagar (Patna), Bengal, Mithila, Kashmir, Nepal etc., and different name were given according to the cradles.
On the way of Script development Primary Nepal script was developed in 9th century, from Kutila script. Nepal script was developed in 10th century. Sharad Kasah, a well known epigraphist notes popular Nepal script (Prachalit lipi), Ranjana, Golmol, Bhujinmol, Pachumol, Kunmol, Kwenmol, Hinmol and Litumol- these 9 types of Scripts can be taken as Nepal's own script i.e. Nepal script. Among these, popular Nepal script was most widely used script which is in use till today (i.e. from 9th to 21st century). This script is more or less similar to Devanagari Script because both were developed from Brahmi script.
Ranjana (Calligraphy) is artistic script. It is also considered as holy script, which developed in 11th century. This script is spread in many countries like India, Tibet, China, Mongolia, Japan etc., specially in Buddhist monasteries. It has thick & thin attractive lining. Thick lined script can mark the paper for longer duration. This script is considered as world's 2nd most beautiful & artistic script. Kutaksyar is a way of writing Ranjana script especially in writing mantras, slogans etc, which, unlike others, runs from up to down.
It is worthwhile noting that scripts are not always related to the particular language. Though many inscriptions and manuscript are found written in Nepal Bhasa, Nepal script was most widely used to write Sanskrit language than Nepal Bhasa. Nepal script was also used to write Maithali language. A few years ago, a book 'Tarka Bitarka' by Nagendra Sharma has been published in Nepali Language in Nepal script. Brahmi script is parallelly related to Pali and Sanskrit. Today including Nepali, other languages : Hindi, Nepal Bhasa, Tamang, Maithali, for instance, are written in Devanagari. Even English we write is in Roman script. So, Nepal script does not belong to particular language or caste. It is the universal script of Nepal.
Source : www.jhinewah.org