Which of the following is NOT a type of number system mentioned?

The correct answer is based on the understanding of number systems commonly recognized in computing and mathematics. The binary number system consists of two symbols, typically 0 and 1, and is fundamental for digital computing. The decimal number system, which includes digits from 0 to 9, is the standard system used in everyday counting and mathematics.

The hexadecimal number system is base 16, incorporating digits 0-9 and letters A-F, widely used in programming and computing for its efficiency in representing binary data.

The trinary number system, while theoretically possible and sometimes studied in academic contexts, is not commonly used or recognized in practical applications compared to the other three systems listed. Thus, it is not one of the main types of number systems that are typically referenced in discussions about binary, decimal, or hexadecimal formats.