ALPHA := %x41-5A / %x61-7A ; Upper- and lower-case ASCII letters (A–Z, a–z)
DIGIT := %x30-39 ; Decimal digits (0–9)
HEXDIG := DIGIT / "A" / "B" / "C" / "D" / "E" / "F" ; Hexadecimal digits (0–9, A–F, a-f)
DQUOTE := %x22 ; Double quotation mark
SP := %x20 ; Space character
HTAB := %x9; ; Horizontal tab
WSP := SP / HTAB ; Whitespace: space or horizontal tab
LWSP := *(WSP / CRLF WSP) ; Linear whitespace (past newline)
VCHAR := %x21-7E ; Visible (printing) character
CHAR := %x01-7F ; Any ASCII character, exluding NUL
OCTET := %x00-FF ; 8 bits of data
CTL := %x00-1F / %x7F ; Controls
CR := %x0D ; Carriage Return
LF := %x0A ; Linefeed
CRLF := CR LF ; Internet-standard newline
BIT := "0" / "1" ; Binary digit