0x1F

0x1F is the hexadecimal notation for the number 31. In computing, it corresponds to the ASCII control character with decimal value 31, commonly called the Unit Separator (US).

In ASCII, codes 0x00 through 0x1F belong to the non-printing C0 control set; 0x1F has no graphical glyph and is used by some data streams to separate fields within a record. In Unicode, the code point U+001F is categorized as a non-printing control character in the C0 range. Its historical role was as a field or data separator in various protocols and file formats, though such usage is now uncommon in ordinary text.

Representation and handling in modern programming: many languages allow representing 0x1F in strings as escapes such as \x1F or \u001F. Some data formats and protocols treat it as a delimiter, while most text-oriented formats sanitize or disallow it due to potential control-character interpretation. In JSON, unescaped control characters below 0x20 are not allowed; U+001F can be included using the escape sequence \u001F.

See also: ASCII, Unicode, control characters.