In the numeral system using digits 0-9 and letters A-F, which system is described?

• A. Binary number system
• B. Decimal number system
• C. Hexidecimal number system
• D. Octal number system

Answer: (C)

This question checks how numeral systems are defined by their base and the symbols they use. The system that uses digits 0-9 and letters A-F corresponds to base 16, called hexadecimal. In hexadecimal, each position represents a power of 16, and the symbols 0–9 represent values 0–9 while A–F represent values 10–15. For example, the hex number 2F means 2×16 plus 15, which equals 47 in decimal. Hexadecimal is common in computing because it compactly represents binary data, with each hex digit mapping neatly to four binary bits. In contrast, binary uses only 0 and 1, decimal uses 0–9, and octal uses 0–7. So the described system is hexadecimal.