The Online World resources handbook

Your first trip online. Typical pitfalls and simple solutions http://home.eunet.no/~presno/bok/v3.html
service. On most bulletin boards, you must enter a command to navigate to the File
Library. Here, they normally greet you with a menu listing available commands.
Try H (for Help!) or ? when you are stuck.
Public domain and shareware programs are stored in subdirectories on my bulletin
board. The directories have numerical names. Utility programs for MS DOS computers
are stored in directory 10. Games are stored in directory 17.
Enter L for a list of available directories (other bulletin boards may use different
commands). Enter "L 17" to list the files in directory 17. This will give file names,
lengths in characters (to help you estimate download time), creation dates, and a short
description of each file.
You can search for files of interest. When looking for programs that can help you get
more out of a printer, you may search using keywords like "printer."
Some programs are made available in text form. This is the case with older BASIC
programs. (The file name extensions .BAS, .ASC or .TXT suggest that the files contain
plain text.) You can download these files using ASCII.
Most programs are stored in their executable form, or as one executable file among
several in a compressed transfer file (a library of files). On my board, most of these files
have the file name extension .EXE or .COM.
What transfer protocol to use, depends on what is available in your communications
program.
The protocol transfer method explained
The protocol transfer algorithms use methods to check the transfer with automatic error
correction. In principle, they work like this:
The sending program calculates a check sum based on the contents of the file. The
receiving program does the same calculation and compares the result with the senders'
check sum. If the figures match, the transfer was successful. If not, all or part of the file
will be retransmitted.
These are some popular protocols:
XMODEM
has automatic error detection and correction. Most modern programs have this feature.
XMODEM exists in programs for MS DOS computers, CP/M computers, Apple, TRS 80
Model 100, etc. It is the most commonly used transfer protocol.
XMODEM assumes 8 bit settings in your communications program. The file to be sent is
split up into 128 bit sized blocks (or "packets") before transfer. The sender calculates the
check sum and adds a check sum bit at the end of each packet. (Packing, sending and
checking is done automatically by the software.)
The receiving program calculates its own check sum and compares with the sender's. If
an error is detected, XMODEM will request retransmission of the last block.
XMODEM is reasonably good when there is little noise on the telephone line is low.
When the line is bad, however, there is always a chance that the transfer will stop. You
cannot use XMODEM on computer networks that use ASCII flow control or ESCape
codes.
The transfer commands must be given to both computers. You can only transfer one file
per command.
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