The Devanagari Script

Introduction

This prelude begins with an introduction to the Sanskrit letters. The writing system used for Sanskrit is known as Devanagari. Indian languages are phonetic in nature and hence the written shapes represent unique sounds. In Sanskrit as well as in other Indian languages, proper pronounciation of the words is quite important. Hence it is necessary to learn the sounds associated with the written shapes.
The word “alphabet” is not usually applied to Sanskrit or other Indian languages. There is a subtle difference between the notion of “alphabet” and the “aksharas” as the letters of Sanskrit are called.  When we think of the word “alphabet”, we normally think of the name given to each letter to identify it. In most languages the letters of the alphabet have names which may give a clue to the sound associated with the letter. In Sanskrit and other Indian languages, there is no specific name given to the letters. The sound the letter stands for is actually the name for the letter. In a phonetic language, reading becomes easy since the reader will be reading out the words by uttering the sound associated with each akshara. More information on this is given in a separate section on Sanskrit and Phonetics.
For many years now, people of the world have learnt the Aksharas of Sanskrit through equivalent Roman letters which employ special marks (known as diacritics). The diacritics, which consist of marks written above or below a letter of the alphabet, refer to variations in the sound associated with the letter. Dictionaries follow his method to help the reader identify the manner in which the word should be pronounced. In India, the National Library at Calcutta has recommended that a single transliteration scheme be used to represent the Aksharas across all the Indian languages. This scheme will be used in the lessons covered in these pages. Students can take advantage of this when it comes to reading text.
The Roman Letters with Diacritic marks will be introduced along with the Aksharas themselves and hence it is not necessary for the reader to have prior knowledge of the Diacritics. A reference to this Transliteration scheme is also available in a separate page. The scheme is similar to the International Phonetic Alphabet representation but has some minor differences. 
Source: Acharya