The admission, magnitude of behavioral modification and effect, as with prefix parameters, depends upon the directive. In some severe cases, the syntax of a directive may be varied to a degree as to invalidate certain prefix parameters; this power especially distinguishes modifiers from most parameters. The two valid modifier characters are @ (at-sign) and : (colon), possibly in combination as either :@ or @:. The following example illustrates a rather mild case of influence exerted upon a directive by the @ modifier: It merely ensures that the binary representation of a formatted number is always preceded by the number's sign: (format T "~@b" 5) Format directives An enumeration of the format directives, including their complete syntax and modifier effects, is adduced below. {| class="wikitable" |- ! Character ! Description |- | |Prints the literal character. Full form: ~repetitions~. No modifier: Prints repetitions times the ~ character. : modifier: Invalid. @ modifier: Invalid. :@ modifier: Invalid. |- | , |Prints a single character. Full form: ~c. No modifier: Prints the format argument character without prefix. : modifier: Spells out non-printing characters. @ modifier: Prepends the readable #\ prefix. :@ modifier: Spells out non-printing characters and mentions shift keys. |- | |Prints an unconditional newline. Full form: ~repetitions%. No modifier: Prints repetitions line breaks. : modifier: Invalid. @ modifier: Invalid. :@ modifier: Invalid. |- | |Prints a conditional newline, or fresh-line. Full form: ~repetitions&. No modifier: If the destination is not at the beginning of a fresh line, prints repetitions line breaks; otherwise, prints repetitions - 1 line breaks. : modifier: Invalid. @ modifier: Invalid. :@ modifier: Invalid. |- | |Prints a page separator. Full form: ~repetitions|. No modifier: Prints repetitions times a page separator. : modifier: Invalid. @ modifier: Invalid. :@ modifier: Invalid. |- | , |Either prints the number in the specified base (radix) or spells it out. Full form: ~radix,minColumns,padChar,commaChar,commaIntervalR. With prefix parameters, prints the argument in the radix (base). Without prefix parameters, the format argument is spelt out, either in English letters or in Roman numerals. No modifier: Prints the argument as an English number. : modifier: Spells the argument in English ordinal numbers. @ modifier: Prints the argument in Roman numerals using the usual Roman format (e.g., 4 = IV). :@ modifier: Prints the argument in Roman numerals using the old Roman format (e.g., 4 = IIII). |- | , |Prints the argument in decimal radix (base