Unicode and ASCII are both character encoding standards that are used to represent text in computers and other devices. Character encoding is a way of mapping numbers to characters, such as letters, digits, symbols, etc.

The main similarity between Unicode and ASCII is that they both use numbers to represent characters. For example, the number 65 means "Latin capital 'A'" in both Unicode and ASCII¹.

Another similarity is that Unicode is a superset of ASCII, which means that the first 128 characters (0-127) of Unicode are the same as the 128 characters of ASCII¹. This means that any text that is encoded in ASCII can also be encoded in Unicode without any loss of information.

However, there are also many differences between Unicode and ASCII, such as:

• Unicode can represent more than 140,000 characters from more than 150 languages and scripts, while ASCII can only represent 128 characters from the English language².

• Unicode can use different encoding schemes, such as UTF-8, UTF-16, UTF-32, etc., to store characters in different numbers of bytes, while ASCII always uses one byte (8 bits) per character¹.

• Unicode is more flexible and adaptable to different languages and writing systems, while ASCII is limited and outdated for modern applications³.