open(filename, mode) : open the given file for reading (mode=="r") or writing (mode=="w"). Return a integer file descriptor which is later used to refer to the file. Returns -1 if the open failed.
close(fp) : close a file.
eof(fp) : TRUE when file is completely read.
read(fp) : read line from the file. Returns "" when the end of the file is reached.
write(fp, ...) : ge extra parameters worden in het gegeven bestand geschreven, gevolg door een newline.
delete(filename) : delete the given file.
rename(from, to) : rename the first filename to the second filename. Will actually perform a copy/delete ifthe rename does not work.
