1 Expressions
 Expressions consist of operands (numbers, strings,  constants,  variables,
 functions, or array elements) separated by:

  o  Arithmetic operators (+, -, *, /, ^, and **)
  o  String concatenation operator (+)
  o  Relational operators (=, <, >, <= or =>, >= or =>, <> or ><, and ==)
  o  Logical operators (NOT, AND, OR, XOR, EQV, and IMP)


2 Truth_values
 In relational expressions, BASIC generates -1 when the  relationship  is
 true  and  0  when it is false.  In logical expressions, BASIC evaluates
 any nonzero value as true; zero is always evaluated as false.  To  avoid
 unanticipated   results,   use  logical  operators  on  the  results  of
 relational expressions.

2 Channel_expression
 A channel expression is a numeric expression that  specifies  a  channel
 number  associated  with  a  file.  A file must be open on the specified
 channel or BASIC  signals  an  error.   A  channel  expression  must  be
 preceded by a pound sign (#).