This statement moves the file mark, in the currently-open file indicated by
fileID, to the end-of-file position (without overwriting any of the existing data in the file). This causes subsequent file output statements such as
print#, write and
write file# to append data to the end of the file.
In the following, note that we open the output file using the "R" method. This is because opening with the "O" method causes the "end-of-file" mark to move to the beginning of the file, effectively erasing any existing data.
A$ = "TESTING..."
open "R", 1, @fSpec // open an existing file
append #1 // set file pointer to end
write #1, A$;25 // add data to end of file
files$; open; close; read#