0xA1

0xA1 is a hexadecimal literal often used in programming and data notation. The 0x prefix indicates that the digits that follow are expressed in base 16, and A1 corresponds to the decimal value 161. In many programming languages, including C, C++, Java, and Python, 0xA1 represents the integer 161.

In character encoding, 0xA1 has a specific mapping depending on the scheme. In Unicode, the code point U+00A1 is the inverted exclamation mark “¡”. In ISO/IEC 8859-1 (Latin-1) and Windows-1252, the single byte with value 0xA1 encodes the same character “¡”. In UTF-8, the character U+00A1 is encoded as two bytes: C2 A1, so the single byte 0xA1 is not a valid starting byte in UTF-8.

In web contexts, the inverted exclamation mark can be represented using HTML entities such as ¡, or numeric references like ¡ or the hexadecimal ¡.

Because 0xA1 is outside the standard ASCII range (0x00–0x7F), its meaning is dependent on the text encoding in use. In environments that assume ASCII, 0xA1 may be undefined or interpreted as a control or extended-byte value, whereas in Latin-1 or Windows-1252 it denotes the character “¡”.

See also: hexadecimal notation, Unicode code points (U+00A1), related byte values such as 0xA0 and 0xA2 in extended encodings.