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)

1  –  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 (#).