Pascal Report  147  3.  Notation and Terminology  declaring  programs, procedures,  and  functions,  in which a block is  given a name (identifier) by which the block may be denoted. Since  procedures and functions may be nested, scopes may be nested.  A procedure or function has a fixed number of parameters, each of  which is denoted within the procedure or function by an identifier  called  theformal  parameter. When a procedure or function is activated,  an actual quantity has to be indicated for each parameter; the quantity  can be referenced from inside the block of the procedure or function  through  the  formal  parameter.  This quantity  is  called the  actual  parameter.  There are four kinds  of parameters:  value parameters,  variable  parameters,  procedural  parameters,  and  functional  parameters.  In  the first case, the actual parameter is an expression  which is evaluated, and the value assigned to the formal parameter,  once at the beginning of each activation of the procedure or function.  The formal parameter represents a local variable.  In  the case of a  variable parameter, the actual parameter denotes a variable and the  formal parameter denotes the same variable during the entire activation  of the procedure or function.  In  the case of procedural or functional  parameters, the actual parameter is a procedure or function identifier.  A function is declared analogously to a procedure, except that the  function yields a result which must possess the type that is specified in  the function declaration. The result type is confined to be a simple type  or a pointer type. Functions may be used as constituents in expressions.  Assignments to non-local variables and other so-called side effects  should be avoided within function declarations.  Syntactic  constructs  are  denoted  by  descriptive  English  words  (meta-identifiers)  written  in  italics  and  are  defined  by  rules  of  Extended Backus-Naur Form  (EBNF)  [Reference  13].  Each  rule  defines a meta-identifier by means of an EBNF expression, which  consists of one or more alternative phrases  separated by  vertical  bars ( I ). A phrase consists of zero or more elements, each of which is a  meta-identifier,  a  literal  symbol  enclosed in  quotes  ("  "),  or an  expression enclosed in  matching braces, brackets,  or parentheses. 