0x7F

0x7F is a hexadecimal literal commonly used in computing to represent the decimal value 127. In hex, the digits 7 and F denote 7×16 plus 15, totaling 127. The prefix 0x indicates hexadecimal notation in languages such as C, C++, Java, and JavaScript.

In ASCII and Unicode, 0x7F corresponds to the DEL control character. In ASCII, code point 127 is the highest value representable with 7 bits; in Unicode it is U+007F. DEL was historically used to erase the previous character on typewriters and teletypes, and it remains a non-printable control character in modern systems.

In programming and data processing, 0x7F is often used as a bitmask to preserve the lower seven bits of a byte: 0x7F equals 01111111 in binary. It also commonly appears as a boundary value for 7-bit data or as a sentinel in certain algorithms, reflecting its status as the maximum 7-bit value. In the context of signed 8-bit integers, 0x7F represents the maximum positive value, 127.

Practical considerations include the historical constraint that a byte is 8 bits, while ASCII characters are defined within 7 bits, limiting text to values 0 through 127. As a result, 0x7F is typically treated as a non-printable control code in modern systems, even though it is a valid 8-bit value in many programming environments.