What is the oldest digital encoding standard used?

The oldest digital encoding standard among the options provided is ASCII (American Standard Code for Information Interchange). Developed in the early 1960s, ASCII was widely adopted for representing text in computers and communication equipment. It assigns specific numerical values to characters, making it possible to represent English letters, digits, punctuation marks, and control characters using a 7-bit binary code.

ASCII's significance lies in its simplicity and effectiveness in encoding the basic English alphabet and special characters, which laid the groundwork for subsequent encoding standards. While newer standards, such as Unicode and UTF-8, have been developed to accommodate a wider array of characters from various languages and symbols, ASCII remains foundational in the world of digital text encoding.

The other options represent standards developed after ASCII. Unicode was introduced later to create a comprehensive character set that supports many languages and symbols globally, while UTF-8 is a variable-length encoding scheme that includes all of Unicode. ISO-8859 is a collection of standards designed to extend ASCII to handle additional character sets, but it, too, came after ASCII's establishment.