What code represents a digit or letter or special character in computers?

In computers, characters, including digits, letters, and special symbols, are represented using character encoding systems like ASCII (American Standard Code for Information Interchange) or Unicode. Each character is assigned a unique numerical code, which allows computers to interpret and display them. For example, in ASCII, the letter 'A' is represented by the code 65, while the digit '0' is represented by the code 48. Unicode extends this system to accommodate characters from multiple languages and symbols, providing a broader range of codes.