Data communications parameters are a
little more critical during file transfer than during normal
chatting. You must have the same settings on the communication
programs on both ends of the line.
Obviously, if you are using 9600
baud on one end, then you should NOT have the other end set up for
1200. In addition, you should check to see whether "line feeds"
follow each carriage return and whether your communications program
is set up to "filter" out certain characters.
Another thing to consider is that
there are different ways of transferring data. These methods are
called "transfer protocols" and the main ones I use are ASCII and
XMODEM. The Ascii protocol is the "Vanilla" of this kind of
communications. It is sometimes referred to as "No protocol".
CompuServe calls it DC2/DC4 Capture protocol. XModem is more like the
double chocolate flavor and is described in more detail later. You
will need to have the same method available on both sides of the
process.
The simplest way to transfer data is
with ASCII transfer. This works fine with text files. Ah, but what is
a "text" file?
A simplistic definition of a text
file is that it can be edited with the Pascal editor and contains
only printable characters. I am not going to attempt a thorough
explanation of the difference between "Text" and "binary" files, but
you may need to understand this area before going too far with RS232
communications. The underlying problem is that some bytes (each
character uses one byte) are used for commands in ASCII protocol and
therefore (a) cannot be successfully transferred and (b) will
probably interrupt the transfer.
The Apple /// operating system (SOS)
assigns a "file-type" to each file. The ones I have seen are
"Asciifile", "Textfile", "Codefile", "Datafile" and "Sosfile". This
"file-type" can be independent of the file name suffix. The preferred
convention is to use a suffix that identifies the file-type and this
is usually done. Files with the suffix ".code" usually have a
file-type of "Codefile" and other suffixes are used similarly.
However, it is possible to assign any suffix to any file and not
knowing this can lead to a great deal of confusion. Just changing the
suffix of a file does not change its file-type.
The word "text" has three separate
uses in relation to the Apple /// files.
(1) The first use is in contrast "text" files with "binary" files,
as discussed above. "Text" files can be transferred with ASCII
protocol, binary files require a different protocol. In general
"text"files can be edited and read as
text while binary files are usually read only by computer programs.
Files with file-types "Asciifile" and "Textfile" are text files.
Files with other filetypes are binary files.
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