ISO Pascal reference manual

Chapter 5
non-occurrence of this message cannot be interpreted as meaning that
statements can be executed.
PROGRAM warn(output);
CONST check = false;
BEGIN
END.
IF check THEN writeln('checking is enabled');
Warning 5 -- check that an empty statement is really wanted here
Certain constructions in Pascal control the execution of a statement, e.g. IF
and WHILE. In such cases it is possible to specify that a null or empty
statement be controlled. This is acceptable Pascal, but the compiler will
issue a warning as it is very likely that the null statement is the result of a
misplaced semicolon.
PROGRAM warn(output);
[this program will only output ONE Line because of the)
[dubious semicolon following the DO)
VAR n:1..10;
BEGIN
END.
FOR N := 1 TO 10 DO;
writeln('Hello there');
Warning 9 -- only the first 253 characters of this identifier
-- will be used
This warning is issued when an identifier contains more than 253
characters. As it is not at all easy to construct a program containing
identifiers of anything like this length, it is highly unlikely that the warning
will ever be issued except from programs which deliberately set out to
generate it.
Warning 19 -- has not been used
Warning 19 -- the field of the record at line
-- has not been used
This warning indicates that < name > has been declared but has never been
used. It is intended to be used to help remove redundant variables and to
22 Pascal Issue 1