The Program Heading and the Declaration Part  25  3.E.  Variable Declaration Part  Figure  3.j  Syntax diagram for  VariableDeclarationPart  Every variable identifier occurring in a program must be introduced in a  variable declaration.  This declaration must textually precede any use  of the variable, unless the variable is a program parameter.  A variable declaration introduces a variable identifier and its  associated data type by simply listing the identifier followed by the  type. The symbol  var heads the variable declaration part. The general  form is:  Example:  Any identifier (denoting an external entity - usually a file) listed in the  program heading parameter list except  Input  or Output  must be  declared in the program's variable declaration part.  Input or Output,  if listed, are automatically declared to be textfiles (see Chapter 9).  program TemperatureConversion(Output);  { Program 3.1 - Example program illustrating constant  and type definition and variable declaration parts.  }  const  Bias  =  32;  Factor  =  1.8;  Low  Separator  =  '  ';  Blanks  type  CelciusRange  =  Low .. High  -20;  High  , . $_{, }$ 39;  { a  subrange type-see Chapter 5  };  var Rootl,  Root2,  Root3:  Real:  Count,  I:  Integer;  Found:  Boolean;  Filler:  Char; 