|D : Dial A Program|
To be capable of down-loading software – shareware or public domain – you will need a modem to talk to the 'host' computer via the telephone line. Reviews of the various modems have appeared in the BBC specific magazines and these should be used to choose a suitable one should you not already have one. Alternatively you may phone Dabhand Computing on the number given in Appendix A for free advice – they can also take your order of course!
At your end, you connect the modem to your RS423 port, and to the telephone line – you must have a BT Type 600 wall socket – and connect your telephone instrument into a socket in the back of the modem. When the modem is not in use, or switched off, the voice telephone line passes straight through, and behaves normally. However, when you dial out to another modem, you can switch the modem on, and the two modems establish contact. At this point the noise on the telephone handset disappears. The two computers are now in communication. Most modern modems will actually perform the dialling and connection for you, so there is no need to use a telephone instrument.
All communications software at this point enters a mode where whatever you type is sent to the remote modem and computer, and whatever it throws back at you is displayed on your screen. (Therefore, to see yourself type, and well the remote messages, the other system must echo everything it receives.)
The bulletin boards which contain downloadable PC software almost invariably use the same communications settings, and you should set your comms software to these:
|Terminal Type: Scrolling or ASCII (not Viewdata)
Parity: None or N
Stop Bits: 1
XON/XOFF : Yes
Files transfers supported: ASCII, XMODEM
Don't worry if there are not options for all these on your menu. As long as you set the first five (and 8,N,1, Full Duplex should be default settings anyway) then everything should work.
Modems works at different speeds. The four main speeds used in this country are:
|V21||300 baud send, 300 baud receive|
|V22||1200 baud send, 1200 baud receive|
|V22bis||2400 baud send, 2400 baud receive|
|V23||75 baud send, 1200 baud receive.|
Baud means bits-per-second. To work out the number of bytes per second, divide the quoted figure by 10 (not eight, as there are two extra bits send with each byte). Naturally, the faster the software, the more quickly you will be able to download software. The snag is that V21 and V23 modems are cheap, V22 modems cost a bit more and V22bis modems cost a lot more. Some modems work at more than one speed, and are altered either by a physical switch, or a software command. The newer ones simply let you adjust your computer's RS423 speed, and alter themselves accordingly.
To check which speed to use, you must check the speeds supported by the bulletin board (virtually always either V21 and V23 only, or V21 and V22 only, or all four) and the speeds of your modem, and in the case of using a real PC, whether your software and modem support the use of V23, and use the fastest available speed. Performing a software download involves a great deal of receiving and very little sending, so V23 should be used in preference to V21, if these are the only speeds available. PC programs are in general much bigger than those on the BBC, and 200k files are not uncommon. Don't worry, virtually all BBC comms software is capable of downloading files bigger than the BBC memory, by spooling them out to disc, but you can't avoid the fact that it takes a long time.
When connected to the bulletin board, you must use a 'file transfer protocol' to download files. The simplest is XMODEM, which is available on virtually all packages. There are two varieties of XMODEM (CRC and Checksum) but don't worry – the software usually sorts out which one to use. All you do is select 'Download' from a menu presented by the remote system, and select a file, and you will be prompted to start downloading. At this point, you invoke the XMODEM download command on your own software (at which point you will be asked for a BBC filename, as XMODEM does not automatically read the remote filename).
The procedure in detail, including setting up a modem, will be given in the manuals which accompany your modem and terminal software. The computer magazines are full of advertisements for modems and terminal software. With modems, the autodial type are preferable, although these are a little more expensive than manual dial. Communications software products such as 'Hearsay' from Beebugsoft, 'Modem Master' from BBC Soft, and 'CommSoft' from SoftMachinery will perform all the tasks described above. These three are specifically mentioned as they also support autodialling modems, allowing you to select a bulletin board from a list of them, and connect with a couple of keystrokes. Note that Viewdata-only software is not suitable for downloading PC programs from bulletin boards, nor are the very simple terminal programs sometimes published in magazines, as many of these do not support XMODEM protocols.
The telephone costs of using a bulletin board are exactly the same as those for making voice calls. It therefore makes sense to use local boards if possible, and to call outside peak hours. You will however find that some boards are constantly engaged from the dot of 6pm, whereas they are available during the day. This is normally the only cost (other than the purchase of modem and software). Note however, that some of the more professionally run boards also charge a small annual subscription, which has to be paid before you can get full access to all the features. The full shareware library is often, naturally, one of the subscriber-only features of these boards.
You will often find that downloadable PC software is supplied in a single file with an extension .ARC. This means that to save download time, the files have been reduced in size using a compression algorithm (a program which encodes the file, with the coded version being shorter) and at the same time, the opportunity has been taken to join all the files needed to run the program into one big file.
The first time you download software, you should look for a file called ARC.COM, or PKXARC.COM, or ARCE.COM or something similar, and download this. Then download the file you want – the one with the .ARC extension – and afterwards, when you have disconnected from the bulletin board, decompress the program. If you run the ARC program without any parameters, ie just type ARC, and press RETURN it will give instructions on how to use it. The normal method is to simply append the filename of the .ARC file, with an 'extract' parameter. So if you had downloaded a file called GAME.ARC, you would type:
A>ARC -X GAME
and all the GAME files would be created. You could then delete the original .ARC file. Obviously, you only need to download the ARC file once. The ARCE variant is a shorter program which only decompresses – it doesn't compress, verify etc. This program doesn't need the -X parameter, so you would type:
When you call a bulletin board, remember that the person operating it (the system operator or 'sysop' for short) is usually running the service as a hobby, without reward, and it is considered polite to contribute as well as taking. Bulletin boards contain messaging sections, where you can ask and answer questions, and also have 'upload' sections, where people can leave programs that they have written, or shareware/public domain programs they have acquired, for the benefit of others. One of the major complaints that sysops have is that the majority of their callers just log on (connect), download every bit of software in sight, and log off (disconnect) without so much as a thank you message.
There follows a small list of bulletin boards, with telephone numbers. These were correct at the time of writing, but as this is essentially an amateur movement, boards close and open all the time, so keep up-to-date by checking computer magazines etc.
These boards are, as far as is known, 24 hours boards, which definitely run at V21 and V22 speeds, and in most cases, V22bis and V23 as well.
|Direct Line||01-841 1847|
|PD Sig||0895 420164|
|Brown Bag Board||01-404 0897|