Explore the World of Software 2: Kids, Adults, Educational

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Text File | 1991-04-02 | 16.7 KB | 288 lines

████████████████████████████████████████████████████████████████ JOY OF MODEMS THE FRUSTRATION IS WORTH THE EFFORT! ████████████████████████████████████████████████████████████████ Two concepts best summarize computer/modem telecommunications: addiction and mild frustration. Put simply, modem communication is perhaps the most addictive, useful and powerful application of a computer - albeit a process fraught with the need for patience and persistence. No pain, no gain, as they say. First let's look at the pieces of the puzzle. Computer telecommunications, simply stated, is the process of hooking one (or more) computers together via a telephone line to exchange files of information and programs or carry on a live conversation. Your computer will need a device called a MODEM which allows data to be converted into a special signal which can be transmitted over phone lines to another computer which awaits the information. There are two types of modems: internal and external. External modems are slightly more expensive than internal modems and are housed in an external box or enclosure. External modems require a socket on the computer or port (usually the serial port on the back of your computer.) The serial port is also called a COM port, com for communications. Most PC's come with a serial port, a few must have it installed. If you are already using the serial port for something else (e.g., a mouse or pointing device) you may need an additional port installed or temporarily unplug the device using the serial port. External modems take up a bit more space and add a bit more clutter (internal modems mount inside the computer.) However some people like the external modem with its blinking lights which instantly displays call status - something a hidden internal modem cannot do unless special display software is also installed or activated. Another consideration is that external modems are portable, you can move from machine to machine by simply unplugging the external modem and taking it home or to the next job site. Next some basic terminology to help things along. The "host computer" refers to the computer your PC is calling. Sometimes this is a commercial service such as The Source or Compuserve which are large interactive services. Other times the host may be another pc your friend is using on the other side of town or perhaps a BBS (bulletin board system) which is a computer operated for general public access by a private individual or company with files and messages of general public interest and access. Another important term is the baud rate associated with the modem transmission process. Essentially baud is a reference to the speed at which your modem and the host modem exchange information. Some common rates are 300 baud, 1200 baud and 2400 baud. A 1200 baud modem is roughly 4 times faster than a 300 baud modem. And since you may be transmitting information via long distance lines, speed and brevity of the modem link is of interest. Some BBS (bulletin board systems) will not allow slower 300 baud modems to load or access software files since this ties up the "board" for other users. As an aside, a 2400 baud modem can be switched to transmit and receive at the slower 1200 and 300 baud rates so there is some "downward" flexibility in purchasing a high speed modem which allows lower baud rates as needed. Curiously the software which controls the modems and computers linking during this exchange will "synchronize" the two modems, determine which modem is using the slower speed and adjust the faster modem downward to a that speed. Many BBS systems use the 2400 baud rate and some are even capable of 9600 baud - in this case the BBS host computer will slow to your rate. If you plan to do much long distance modem work, the 2400 baud modem is the wisest choice. The somewhat higher initial purchase price which will obviously be offset by savings in reduced long distance rates. Next we dip into the software pool. While DOS controls the internal workings of your computer, you'll need communications software (sometimes called terminal software) to enable the pc, modem and telephone line to work together. Many commercial software packages have a communications package built in or added as a separate module. Shareware and public domain packages also exist (which are themselves obtained from BBS systems via modem!). Some of the more dependable software packages include Qmodem, Procomm, Boyan, Telix, and GTpowercom. Good communications software is flexible and powerful without being difficult to start and use. The best packages have help screens and tutorials as is common with application software in general. Telix, for example asks a few simple setup questions then attempts to set the variety of numerical settings needed without operator intervention or frustration. The favorite modem software package for the author of PC-LEARN is the shareware software product: TELIX. Although baffling at first, the modem software setup process allows configuring the software package to your specific PC and modem. The modem software needs to be told if you are using serial port (com port) one or two. You will need to tell the communications software which directory or drive where files will be sent or downloaded. The baud rate must be set as well as noting if the modem is Hayes compatible. Hayes compatibility refers to a standard set of transmission instructions which many modems share. In some ways this is similar to the DOS standard within operating systems for IBM compatible computers. The modem software must also be told other basic details such as PARITY, and DATA BITS which refers to how the data is "grouped or packaged" during the actual modem transmission. Generally data bits are set to 8. Parity is usually set to NO. Commercial services such Compuserve offer exception to these settings and will tell you these settings in their literature. An example: If parity is required, set data bits to 7. Set stop bit to 1. This is a total of 1 + 7 = 8 Bits. The final bit is usually used to check parity/accuracy. The above setting is somewhat cryptically referred to as 8N1 which means 8 bits, no parity, one stop bit. Don't worry about this too much now - frequently this is a one time setup which you will not have to fiddle with once the software has been set. Other settings can include ANSI standard terminal emulation (a standard selection you should check if given the choice). ANSI terminal emulation is usually the default setting and should only rarely be changed. PROTOCOLS must also be specified. In simplest terms a protocol is a method of checking for errors between modems as the data transmission progresses. In a precise fashion, these protocols tell the first modem to transmit a small packet or "chunk" of data then the receiving modem will play back a short verifcation "checksum" or "password." The transmitting modem stops, listens for the checksum and if that item matches the information which it sent, the first modem then transmits the next packet/chunk of the message. This continues, one small chunk of data at a time. The concept here is to protect data integrity over noisy, static-prone telephone lines. UPLOADING data to the host (you transmit data to the other computer) and DOWNLOADING data (you receive data from the other computer) requires selection of a protocol method. Several common protocols include Xmodem, Ymodem, Xmodem-CRC and Zmodem. Xmodem is generally offered by most BBS systems and is a safe bet if you are not sure. Other protocols are somewhat faster and/or slightly more dependable, but Xmodem will usually do the job. Trial and error or simply logging onto the BBS system with Xmodem and then inspecting the menu of other protocols available will give you more detailed information and clues about other possible protocols. Ymodem offers a faster transmission rate than Xmodem, better data security through a refined CRC checksum method and finally a method for "batching" or sending/receiving several files one after another unattended. Zmodem is faster still, somewhat more secure with respect to data loss, likewise offers batch transmission of many files and additionally allows a file to be partially stored if transmission connections are lost and then completed when the connection is restablished so you do not have to transmit the entire file again! General considerations in selecting software for modem use include: * The dialing directory is of crucial importance. The idea is that the package will store and dial your most frequently dialed numbers. Some packages hold only a few, some quite a lot! Does the package store your individual password and comments next to each number? You may wish to use different passwords for each BBS system you call. * Consideration of transfer protocols offered. Xmodem is a basic, but you may want more efficient protocols later. Make sure the package supports several or can be upgraded to more protocols later. Zmodem one is the best at the time this tutorial was prepared. * How does the package dial numbers from the list? Will it call back and continue trying? Can it dial numbers from the list in a certain order. Can it do circular dialing (several numbers are called in a row, then the program jumps from the bottom of the list and starts at the beginning again - around and around in a circle)? This type of dialing efficiency is important if you deal with busy communications services and BBS systems where it may take time and several attempts to log on to a system especially during the busy evening peak time. * Does the package offer scripts or macros? Simply stated a script is a way of having the package automate several steps. Without further input the package can call a BBS system, type in your password and then continue typing further keystrokes as if you were entering them from the keyboard yourself - in essence a script capability is a programming-like language which gives the communications software package a customized way to enter many keystrokes while you only input one or two strokes to start the chain reaction. Many programs let you even record the sequence of keystrokes during a communications session for playback and retrieval later. Beware though, if the system which you are calling changes log on sequences or you may have to go back and later revise your original script - not a major problem, just a concern. * Is it possible to capture screen information to your disk drive? Can you output screen information to your printer? Long communication sessions on line with your modem produce endless screens of information which scroll by quickly. The ability of your software package to output all or selected parts of your session to permanent disk file or printer output can be a tidy bonus. Local neighborhood BBS systems can offer the most entertainment and information for the first time user. The cardinal rule of behavior: "act as if you are in someone else's home." Courteous behavior is a must. How do you find telephone numbers for these systems? Consult local computer clubs for a few numbers for BBS systems and then call the BBS systems with your modem for lists of MORE local telephone numbers. BBS operators and users are quick to answer questions for new users and can serve as helpful "experts" on any computer question no matter how arcane. Operators of these BBS systems are frequently call SYSOPS and many provide BBS systems as a hobby activity much as other hobbyists enjoy short wave radio operation. Most BBS systems will allow you to tour within the various activities and parts of the system for 30 minutes to an hour on your first call. After that you are expected by some "boards" to leave your name and a phone number where you can be reached for verification. Some boards are free, some request a nominal use fee (usually around $25 per year.) Some boards request that you upload (send to them via modem) shareware files or public domain software in order to download their software. The process is something like two kids with bubble gum trading cards: "I'll trade you 125,000 bytes of this shareware file for 200,000 bytes of your files." On your first visit into a BBS board you usually are allowed access only to certain "low level" but interesting areas of the BBS "board." The SYSOP (system operator) may be available to come "online" if you experience difficulty. The software of the BBS system itself will safely keep you from damaging the host computer even if you hit an incorrect key or enter an erroneous command. You may leave messages for the SYSOP, leave messages of a general nature, ask for help on a specific question, download public domain software, play a game, or just generally explore the information within the system of the host computer. Downloading files is easy. For many boards the command is a simple "D" for download. The BBS will ask you the name of the file you wish to download and then give you an estimate of how long it will take and the modem protocol you will (or should) be using. After that you key in a keystroke or combination which tells the software in your computer to begin the process. When the transfer is complete, the host BBS takes over and presents the main menu of choices or selections - in essence you can continue to browse as before. Lists of phone numbers for online services and BBS numbers are available from the boards themselves and many local newsletters of computer clubs and many computer store salespersons. Most public domain and shareware software from BBS systems is stored and transmitted in a compacted form of either an ARC or ZIP format. You will need a small public domain program (ARC or NARC or PKZIP) also available from the BBS board to unpack the software. This archiving or "arcing" process is done to compact the software for shorter, more efficient transmission - it saves time and disk space for both the BBS host computer and your computer. The easiest way to visualize arc'd or zip'd software is to think of the many files of a typical software package compacted in size and then placed into one single file. You might also wish to compact your other files for storage on a hard drive aside from the modem process. File compaction is a useful tool unto itself! ARC and ZIP software are shareware packages available from BBS systems. Working with modems and telecommunications software sounds arcane and daunting at first, but it is a thoroughly enjoyable and rewarding pastime - and also a nice way to make friends and delve deeper into the global network of information and friendships this new form of communication represents.