To deliver information efficiently, it is necessary to use at least a modest set of easily understandable characters. For many human languages, including English, the most relevant of these would be letters in upper and lower case as well as punctuation marks. Representing them requires assigning a numerical value to each character within a chosen set. Thus, the purpose of encoding characters is to provide means to represent digitally stored data as text.
Moreover, transferring information requires that the numerical values assigned to certain characters would remain the same on different devices (Gala, 2021). It necessitates the creation of universally shared and accepted character encoding standards, such as ASCII or Unicode, to ensure that the same combination of symbols would always be displayed correctly.
ASCII, which is short for American Standard Code for Information Interchange, and Unicode are the two most used character encoding standards in the world. ASCII represents 128 symbols, including uppercase and lowercase English letters (Gala, 2021). On the other hand, Unicode has a much broader scope and represents symbols from a wide variety of existing and dead languages (Gala, 2021). As a result, Unicode only uses 7 bits to encode each of its characters, while Unicode’s UTF-8 can use up to 4 bytes per character. At the same time, Unicode’s first 128 characters correspond exactly to those of ASCII in the interests of compatibility (Gala, 2021).
Thus, the main difference between these two encoding standards is their scope and the number of characters they portray. For practical purposes, one may view ASCII as an incorporated subset of Unicode that covers the most-used symbols, including English letters and common punctuation marks.
Reference
Gala, J. (2021). ASCII vs. Unicode. Geeks for Geeks. Web.