ISO Pascal reference manual

*ERROR 31 -- this expression has not been formed correctly
This message indicates that the compiler cannot make any sense of an
expression.
*ERROR 32 -- is a procedure and may not be used in
an expression
Appendix A
The name of a procedure is not a valid operand in an expression as a
procedure call does not return a result. Procedures may only be called or
passed as parameters.
PROGRAM fail;
VAR j : integer;
PROCEDURE twenty;
VAR result : integer;
BEGIN
result := 20;
END;
BEGIN
j := twenty; (wrong)
END.
*ERROR 33 -- must be followed by a boolean expression
This error indicates that the given < item > is only meaningful if followed
by an expression which gives a boolean result but no such expression has
been found.
PROGRAM fail(output);
VAR x : integer;
BEGIN
x := 1;
IF x THEN writeln('oops'); (x isn't boolean)
END.
*ERROR 34 -- the operand to the left of must give a boolean value
The reserved words AND and OR may only follow a boolean operand. In
particular they may not be used to form conjunctions or disjunctions of bit
Pascal Issue 1 55