output, often consuming one or more format arguments. Directives A format directive, introduced by a ~, is followed by zero or more prefix parameters, zero or more modifiers, and the directive type. A directive definition, hence, must conform to the pattern The directive type is always specified by a single character, case-insensitive in the case of letters. The data to be processed by a format directive, if at all necessary, is called its format argument and may be zero or more objects of any type compatible. Whether and in which quantity such data is accepted depends on the directive and potential modifiers applied unto it. The directive type ~%, for instance, abstains from the consumption of any format arguments, whereas ~d expects exactly one integer number to print, and ~@{, a directive influenced by the at-sign modifier, processes all remaining arguments. The following directive, ~b, expects one number object from the format arguments and writes its binary (radix 2) equivalent to the standard output. (format T "~b" 5) Where configurations are permissive, prefix parameters may be specified. Prefix parameters Prefix parameters enable an injection of additional information into a directive to operate upon, similar to the operation of parameters when provided to a function. Prefix parameters are always optional, and, if provided, must be located between the introducing ~ and either the modifiers or, if none present, the directive type. The values are separated by commas, but do not tolerate whitespaces on either side. The number and type of these parameters depends on the directive and the influence of potential modifiers. Two particular characters may be utilized as prefix parameter values with distinctive interpretation: v or V acts as a placeholder for an integer number or character from the format arguments which is consumed and placed into its stead. The second special character, #, is substituted by the tally of format arguments yet abiding their consumption. Both v and # enable behavior defined by dynamic content injected into the prefix parameter list. The v parameter value introduces a functionality equivalent to a variable in the context of general programming. Given this simple scenario, in order to left-pad a binary representation of the integer number 5 to at least eight digits with zeros, the literal solution is as follows: (format T “~8,'0b" 5) The first prefix parameter controlling the output width may, however, be defined in terms of the v character,