ISO Pascal reference manual

*Execution error -- REWRITE required before write access
This error is caused by an attempt to write to an input file. Before the data
in an input file may be accessed the file must be made an output file by
calling the procedure REWRITE.
PROGRAM error(output);
VAR f : text;
BEGIN
END.
rewrite(f); (create it}
writeln(f, this is a line'); (fill it}
reset(f); (make it input}
writeln(f, 'oops'); (wrong}
writeln('Error not detected');
*Execution error -- EOLN invalid at EOF
This error is caused by calling the Boolean function EOLN when the file is
at end-of-file (EOF). The function EOF(file) should usually be tested before
EOLN to avoid this error.
PROGRAM error(output)
VAR f : text;
BEGIN
END.
rewrite(f);
writeln('one line');
reset(f)
readln; (nothing left in f now}
IF EOLN(f) then writeln('end of line');
writeln('Error not detected');
*Execution error -- invalid number syntax
This error is caused by an attempt to read a numerical value (integer or
real) from a file if the input cannot be interpreted as a number. Note that
the Pascal standard only permits spaces and end-of-lines to be skipped
before a valid number is found. In particular a comma will not be skipped
and will invoke this error.
110 Pasca] Issue 1