System

IOResult returns the result of the last Delphi I/O routine when I/O-checking is off (that is, when using the {$I-} compiler option). If IOResult returns 0, the last I/O operation succeeded. Otherwise, IOResult returns an error code. 

If an I/O error occurs and I/O-checking is off, all subsequent I/O operations are ignored until the internal error flag is cleared. Calling IOResult clears the internal error flag. 

An alternative way to handle I/O errors is to use exception handling with the {$I+} compiler option.