The most fundamental unit of information in a digital system is:

The most fundamental unit of information in a digital system is the Bit. A bit, short for binary digit, represents the smallest piece of data in computing and can only have one of two values: 0 or 1. All digital information, from complex programs to simple text, is ultimately stored and processed as sequences of bits.

• A Byte (B) is a collection of 8 bits. While a very common unit for measuring data, it is composed of multiple bits and therefore not the most fundamental.
• A Kilobyte (C) is approximately 1,024 bytes, representing a much larger quantity of information.
• A Gigabyte (D) is an even larger unit, roughly 1,024 megabytes, or billions of bits. These larger units are used to quantify significant amounts of data storage or memory, but they are all built upon the foundational bit.