Frostbyte's 1980s DOS Shareware Collection/floppyshareware.zip/floppyshareware/GLEN/SLICK48.EXE/TELECOMM.TXT

Text File | 1991-06-22 | 38KB | 519 lines

    From Simple Software Company....................producers of SlickWare !

                     Telecommunications for the Beginner
                               by G.M. Raymond

    Welcome  to the world of Slick Communications. This text is intended for
    the new telecommunicator who is interested in learning about  the  world
    of  modem  and  computer  communications. Perhaps you have already heard
    about modem telecommunications and  just  want  more  information.  This
    article will tend to serve the needs of either person.

    Your  first  question may be "Just what is a Modem good for ?". The most
    common use is to access other computers. This could be to exchange  data
    with  other  computers  within a company or to access computers of other
    individuals or companies. This computer connection can be  made  via  an
    ordinary  telephone  system  or  on  a  special  leased line or network.
    Perhaps the most ordinary use today for individuals,  is  to  use  their
    modem to call other private or commercial systems, known as BBS's (short
    for  Bulletin  Board  Systems).  These BBS's provide a place for program
    writers to market their products (called ShareWare)  and  an  electronic
    mail  forum  for  messages,  questions,  and  anything  of  interest  to
    telecommunicators.  Most people elect to download programs. We will talk
    more about that later.

    First, lets get a handle on terms and definitions.  To  communicate  via
    voice, be it wire or radio, it is necessary to MOdulate our voice signal
    onto the electrical current carried by wire or radio wave.  Then, on the
    receiving  end,  DEModulate  the  current  back into intelligent audible
    sound waves. Essentially we do the same thing with a computer.  We  take
    data and send it out and reinterpret it on the received end. So, this is
    the job of the MODEM.  The humble modem is actually a very sophisticated
    piece   of   elec-tronics.   Just   as   standardization  took  hold  of
    broadcasting, with AM and FM dominating the  available  channels  today;
    there  has been a slow but consistent push to standardize the methods of
    exchanging data between computer modems. First,  you  should  understand
    that the modem, like the computer itself, is just a dumb machine. It too
    (the  modem)  need  a  soft-ware program to operate. These are generally
    referred to as Terminal programs or comm software.   Naturally,  we  are
    partial  to  SLICK  terminal  because  we sell it. Fortunately, most all
    modems still being manufactured today, use a set of instructions  called
    Hayse  commands  which  have  more or less become the industry standard.
    Most all modems and software  found  on  todays  market  will  have  the
    necessary  configurability  to  adjust  to  each  other  as  well as the
    computer. We need to talk about this more.

    Your modem will connect to your computer via a connection referenced  as
    a  serial  port. It might be interesting at this point to state that any
    external peripherals (printers, modems, monitors etc.)  will  attach  to
    either  a  serial  or  parallel  interconnection.  The  basic difference
    between the two methods lies in how the  signal  is  moved  through  the
    cable.   In  a  serial connection, each bit of data is sent sequentially
    (that is, one after another). It takes 8 bits of  data  to  represent  a
    single  character  of  which  there  are  255  characters in total. (The
    alphabet and most common punctuation are in the range of ascii  [decimal
    33]  to [decimal 127]). So, with a serial connection, eight signals must
    pass to have one character arrive on the other end. By comparison,  with
    a  parallel  connection,  all  eight  bits  are  sent  together on eight
    separate wires in the cable. With this system,  each  character  arrives
    intact  and  almost eight times faster. The parallel method is ideal for
    supplying devices like printers with input data because  of  its  speed.
    The  biggest  drawback  is  signal  attenuation  when trying to use long
    cables (i.e.,stay under 12 feet) and finding accurate  method  of  error
    checking  the  integrity  of  the  data  sent.  (i.e.  did a character Z
    actually arrive as a "Z"). Sending data serially has  certain  drawbacks
    when  it  comes  to this error checking procedure.  Several methods have
    been developed that have become standards. If you are only interested in
    sending the alphabet, you do not need the full byte or all  eight  bits,
    only  seven  will do nicely. This is because the decimal value of 127 in
    binary form is 0111-1111, requiring only 7 bit positions. Starting  from
    right  to  left,  each  of  these  bits  represents  a  decimal value of
    1,2,4,8,16,32, and 64.  The sum of these bits equals 127.  If  the  left
    most  bit  were to be used (1111-1111), its value alone equals 128 so by
    using 8 bits all 255 characters could be encoded and  transmitted.  That
    is, a range of values from zero (0) to 255. (Yes, zero has a value). The
    bottom  line,  7  bit rate transfers are faster but useful only for text
    data.  (sometimes referred to as low ascii- [under 128]). On  the  other
    hand,  the  eighth  bit  can be useful for parity checking which we will
    discuss later.  If we were to actually use the  8th  bit  for  character
    data this would eliminate parity verification. Hence a setting of 7E1 is
    useful  for character (English text) only. This also precludes a setting
    of 8E1 or 8E2. Yes, the 7 is the number of data bits used, the E, O or N
    indicates the use of parity or NO parity.  The one (1) is for the number
    stop & startbits.

    EXE Files are made up of ascii characters throughout  the  entire  ascii
    range  of  zero  through  255. (yes, zero is a value to be counted....in
    fact the computer could not survive without it). Just to  be  safe  then
    with  only a small sacrifice in speed, 8 data bits is the way to go. The
    next consideration is also one of protocol. Do we use 1 or 2 extra  bits
    to  signal  the  start  or stopping point of the group of 8. There is an
    argument that can be made that two are more reliable  than  one  but  it
    also can be said the loss in double the transmitting time isnt worth the
    extra  margin of accuracy. By preference, most choose only 1 stopbit for
    their protocol. Now we have to talk about parity. This is  nothing  more
    than  a  simple  way  of  testing  each  character  for  accuracy on the
    receiving end. There can be either EVEN, ODD or  NO  parity.  Parity  is
    simply  a  checking  of  the  transmitted  bits  per byte (character) to
    determine if the seven positions make up an odd or even number.  A  zero
    is  used  as the eight bit if the other seven result in an ODD number of
    ones and a 1 (one) is used to indicate an  even  number.  i.e.  01000001
    (normal  capitol  A)  becomes  11000001,  when parity is set to ODD. The
    reverse is true for EVEN Parity. (0 means even) Parity checking  is  not
    only  time  consuming  but  also inefficient. It is rarely used today on
    anything but older DEC mainframes. Finally, we arrive  at  8-N-1.  Eight
    bits, No parity, and 1 stopbit as the desired order of doing business.

    The IBM Personal Computer or clone has various  internal  addresses  for
    its four normally available serial ports. We reference these as COM1,2,3
    &  4 but this is not in-fact the actual location pointer required by the
    hardware. $3F8,$2F8,$3E8 and $2E8 are the correct  locations  for  these
    ports  as  defined in their hexadecimal format. (a number system using a
    base of 16 to represent larger decimal  values  in  smaller  numbers  of
    bytes,  i.e.   65,536  is equal to FF-FFh [a two byte value]). Next, you
    must determine what Interrupt Request line is to be used internally with
    each   comm   port.    The   usual   arrangement   is   COM1,$3F8&IRQ-4;
    COM2,$2F8&IRQ-3.   Seldom  will  you  use  more than two comm ports on a
    system although it is not out of the realm of  possibility.   It  really
    doesn't  matter  what port address you use on a modem until you begin to
    use other serial ports for devices like mousses or null modem cables (to
    link up two CPU's by cable). With more than one serial connection, it is
    sometimes important what device goes on what port as well as having them
    properly addressed in order for everything to work together smoothly.  A
    good modem will have either switches or jumper pins for you to  tell  it
    what  comm  address it is looking for and with what interrupt.  There is
    also a redundant process  here  because  you  must  also  configure  the
    software to operate with the same values.

    Probably the biggest headache of all is setting the software to tell the
    modem  what it wants after you determine what the modem normally sets up
    as defaults to begin with. We are talking  about  the  various  internal
    registers  of  the  modem  that  hold  instructions.   Every  modem will
    initialize with a pre set factory designed default setting.  Very  often
    it happens that a good modem will default to all the correct settings on
    its  own  and you are just wasting your time re coding an initialization
    string that will only repeat for a second  time  the  built  in  factory
    settings.  Here,  several of the more important registers to think about
    are the CD and DTR registers. Normally you want  software  control  over
    these  and  NOT  have  them  forced  on  by  either dip switch or jumper
    settings.  Most all problems related to  problems  with  hanging  up  or
    auto-answer  can be traced to these registers. If your modem defaults to
    &C1 and &D2, great. If not, you need to set them. (via the  hardware  if
    able and or software modem initialization string.)

    Here are some other recommended settings and what they accomplish.
        M1 ..... Speaker On for Dial,Carrier Detect,HandShake and Result
                 Code, then off as DATA begins.
        V1 ..... Verbal Result Codes (CONNECT 2400 rather than a "3")
        X4 ..... Show All Result Codes
        E0 ..... NO local modem Echo of characters. (The host does this)
        &C1 .... Software control of Carrier Detect Status
        &D2 .... Software control of Data Terminal Ready state.
        S7 ..... DTMF (touch tone) dialing speed (usually 70ms aprox is ok)
        S0 ..... set this to 0 to prevent your modem from answering your
                 phone line or X to the number of rings before pickup.

    This will give you a good idea but please remember, when all else fails,
    read  the modem manual. It might be a good point now to bring up another
    related subject. Most computers will  not  respond  to  the  high  order
    graphics  and ANSI color signals without the short program (found in the
    DOS diskette) called ANSI.SYS placed where it can be  read  after  being
    called  via  a  statement  in the computer CONFIG.SYS program. The added
    line to the  SYS  file  is  simply  DEVICE=C:\PATH\ANSI.SYS.  Of  course
    substitute  PATH  for  the  actual directory path to the location of the
    ANSI.SYS file. This  will  allow  monochrome  systems  to  receive  ANSI
    graphics  and  at  least  see  the  graphics if not the color, and color
    systems to come alive. My hats off  to  the  guys  who  can  write  good
    quality ansi graphics for they are truly artist as well as programmers.

    It  might  also  be  wise to mention that the only difference between an
    internal modem and an external  one  is  the  price.   There  is  little
    advantage  in  my  mind  in using external modems. Aside from their cost
    increase due to the necessity of having a built in power supply plus  an
    external  case  they  are  more apt to both receive interference (due to
    poorly shielded cables) as well as generate RFI. Since most PC  have  at
    least  two  or  three  expansion  slots  left  over  after  over zealous
    purchasing, there is usually plenty of room inside the computer case  to
    install  the  modem. This is usually nothing more than slipping the card
    snuggle into an available slot and using  one  screw  to  secure  it  in
    place.   There  are usually two modular jacks on the back, the upper one
    for cabling to the phone line source and the second for  plugging  in  a
    regular phone for whatever use you may have of it.

    Assuming  all  has  gone well at this point you are ready to boot up the
    computer and run the software. Most all terminal  programs  first  clear
    all  registers  with an ATZ command then send the initialization string.
    Unfortunately a lot of programs either  blank  the  screen  during  this
    process  or  simply  don't  allow  the bytes to appear on screen in this
    phase. I am against this kind of design because you never  know  if  the
    modem  swallowed  the string without spiting it up. Meaning, accepted it
    and set registers accordingly or rejected it with an ERROR rather than a
    friendly "Ok" reply. The error always indicates that one of the commands
    in the modem string is unfamiliar to that brand. This either  means  its
    hardware  controllable  only (Dip Switches,etc) or not an option of that
    brand of modem. If just ONE command is at fault, the  entire  string  is
    rejected.   Most  modems  will  accept  up to 40 characters in a command
    string but some will go as high as 255.

    If you are preparing to buy a modem for the first time, be careful. Like
    any products, there are good ones and buggy  one.  Sticking  with  Brand
    names  usually is best and although most modems are being made overseas,
    there are several US and Canadian companies making superb  products.  If
    you want the latest state of the art, look for a modem that supports the
    newest  error checking and compression technique called MNP-5 (for Micro
    Comm Network Protocol, level 5). Finally, if you can  afford  it,  there
    are  several  high  speed modems around that run at 9600 baud or better.
    The high speed models almost always  work  at  all  the  lower  standard
    speeds  as well. But, in any case, don't buy anything below 2400 baud. I
    say this because the price  may  be  tempting  as  there  are  companies
    selling  older  300/1200  baud  rigs for well under fifty bucks. So what
    DOES modem speed have to do with anything ? Well, if your one  of  those
    folks  fond of quoting "Time is Money" you can certainly save a lot with
    a faster modem. Let's see what happens here.  First of all,  what  is  a
    baud  or  baud rate ? Its the number of BITS per second capable of being
    transmitted. Now, if an average sheet of paper is 80 columns across  and
    66  lines  deep  this  counts out to exactly 5280 characters per page if
    completely filled. Now remember, each character may require 7 or 8  bits
    to  construct.  Then  we need the extra stop bit, parity bits if any and
    framing bits. We might end up with as many as five additional  bits  per
    character  by  the  time  they  are  formatted for transmission. So, for
    argument sake, use the value 12 bits X 5280 characters. This  is  63,360
    bits. If we send them at the rate of 300 baud this will take (63360/300)
    seconds.  Or  about  210  seconds or 3 and one half minutes. At 1200baud
    it's four times faster or only 52 seconds.  At the  2400  baud  rate  we
    half  this  down  to  around  25  seconds. Since an average text page is
    really only half the maximum characters  available  this  means  in  one
    minute  at  2400  baud  you could transmit four normal business letters.
    Since AT&T is not free and they have both minimum and time  based  rates
    on  toll  calls,  there is no question that under some situations a high
    speed modem could easily pay for  itself.   The  average  size  programs
    today  run  between  30  and  70k.  (each k equals 1024 bits). Most good
    modems running at 2400 baud will average about 4 seconds per k.  Why did
    I use the word average ? Well first of all, I left out a lot  of  detail
    that  might  have  technocrats pulling out their hair.  In any case, its
    neither my ability or intention to get too technical here but since were
    into speed somewhat as  a  subject  of  exploration,  let's  talk  about
    SLOWDOWNS.   Remember  earlier  we  discussed a parity check at the byte
    level for catching errors ? We said that in most cases it was no  longer
    used.   Well, the reason for that is due in part to more elegant ways of
    catching errors. Probably the first and simplest of all methods  is  the
    CHECKSUM.  Remember, the setting of each one of the eight bits of a byte
    (zeros or ones) determine its decimal (and character) value up  to  255.
    So,  every  byte has a decimal value as well as a character value. (i.e.
    capital A is decimal 65). With two bytes we can carry a decimal value up
    to 65k. This means we could sum the value of 255 characters and send the
    total in two bytes of data. If the sum on the received end  is  not  the
    same  as the previously sent checksum value, the packet is rejected with
    a NAK and a request for retransmitting is made.  By limiting the  packet
    size  to 128 bytes shorter transitions of interference (line noise, etc)
    wont cause bigger delays due to retransmitting of  large  packets.  This
    gives  rise  to a common mistaken idea that while monitoring a download,
    and errors are reported by the  protocol  software,  that  the  file  is
    corrupted.  No, it only means that for every error it cost you more time
    to receive the same packet without error by retransmitting. In any case,
    CHECKSUM was how it began and IT'S STILL HERE.  I guess that speaks  for
    its  staying  power.  But, like everything, it has been greatly improved
    upon.  Now Cyclic Redundant Checking, or simply CRC  protocols  are  the
    rage.  Its more difficult to explain in simple terms but the bottom line
    is a CRC value is calculated for each packet  transmitted  and  compared
    with  what  is calculated on the received end. Again the two must agree.
    The accuracy derived from CRC methods lies in its ability to pass  every
    bit  through  a  16 (or 32) bit shift register that does an Exclusive OR
    with the 6th,8th,11th and 15th bit of the  16  bit  register.  Each  bit
    causes  the  value  of  the register (which can be expressed in four hex
    numbers) to change to a new value. By the time the last bit is processed
    a number is derived that represents a CRC value for the  ordered  group.
    This  method  is almost infallible.  The method was originally developed
    to test the accuracy of the bit content (program) stored in the ROM's of
    the PC. Programmers specializing  in  writing  transfer  protocols  soon
    began  to  incorporate  it  into  their  creations. Now, its used almost
    exclusively.

    There are several ways to ask a modem to dial a number for you.  You can
    do it manually or call  a  number  from  a  previously  created  dialing
    directory that is accessed by the software. To do it by hand simply type
    ATDT  followed by the number if you have Touch Tone Service. Or ATDP for
    pulse dial.  The string will look like  this:  ATDT288-6550  (note,  the
    modem     ignores     the     hyphen).      Or,     if     it's     long
    distance....ATDT1-504-288-6550.  Suppose you wish to defeat Call Waiting
    for this call only (if left on, it can cause  trouble),  the  string  is
    ATDT*70,288-6550.   *70  is the AT&T temporary disable wait instruction,
    the comma is a modem 3 second delay command before continuing  with  the
    dial.   (this allows time for the command to be received and for AT&T to
    give back a dial tone). After entering your dial string you should  hear
    the  modem  taking  the line off hook (signaled by the appearance of the
    dialtone in the speaker), the DTMF dial pulses going out,  the  ring  or
    busy  tone  at  the destination number followed by the host modem answer
    tone and handshake, followed by a CONNECT message on your  screen.   The
    standard  for  a  plain  CONNECT  is  a 300 baud logon. CONNECT 1200 and
    CONNECT 2400 are self explanatory.  Some  host  systems  require  a  few
    carriage  returns  before  you  will see anything on the screen but most
    will automatically begin displaying after the connect message.  Most  of
    the  people  who  operate BBS's are hobbyist. It's another form of hobby
    and social activity all rolled into one similar in a lot of ways to  ham
    radio.   Few Boards will give you total access to everything immediately
    but there are exceptions. Most will request your  real  first  and  last
    name,  a local phone and address, (or out of state,if that be the case).
    Some SYSOP'S (SYStem OPerators[the guy who owns or manages  the  Board])
    will even phone you back to verify at least your phone number. Some have
    even  more stringent requirements, but, most will simply give you access
    next time they  sit  at  the  console  and  get  caught  up  with  their
    duties.(usually  24  to  48  hours).  When BBS's first cranked up in the
    earlier eighties,  Sysop's  were  sort  of  groping  along  to  try  and
    determine  what  their users wanted. The use of phoney names and cloaked
    identity was very  common.   The  misuse  of  BBS's  for  a  while  even
    threatened  their  legality  as  so called hackers exchanged information
    they newly acquired. Most of this was in the form of either passwords to
    big mainframes,  private  telephone  code  access  numbers  and  pirated
    software.   Fortunately,  BBS's  have  grown  up  and  matured into very
    legitimate forums of information exchange. To this day I  still  do  not
    have  a  clear  understanding  of the word Hacker. It seems to mean many
    things depending on who you are talking to. Hardly any Sysops run Boards
    that they wrote the program for. They usually use a  commercial  product
    that  seems  to  best fit their own idea of what a Board should be like.
    Sometimes they simply fall victim to a  bad  recommendation  from  a  so
    called  expert  or  seasoned  user.  If nothing else, one thing you will
    learn quickly in this business is that there are a great  deal  of  self
    proclaimed  experts.   What's really funny is the true complicity of the
    machines vrs the real depth of knowledge of  most  of  these  so  called
    experts.  I think the old saying "A little knowledge is dangerous..." is
    most  appropriate here in computer land. Lots of the questions that come
    pouring fourth when attempting  to  gain  registration  as  a  user  are
    therefor  not  the  creative  genus  of  the  Sysop  but rather the dumb
    invention of an other- wise great  code  writer  who  had  to  think  up
    something  to  ask  during that phase of Logon. (Logging Onto a System).
    One of my personal gripes is the Sex, Age questions.....why not race too
    and make it a total violation of first amendments rights.  Anyway,  like
    it  or  not,  you have to comply with the rules if you expect to get and
    stay in the game.

    Most Boards allow some limited ability on first Logon, like reading  the
    Bulletins  and  E-Mail  (Electronic Mail). A Menu will appear giving you
    the choices available. Since it's well known that 99 % of all registered
    users only check in to see what's new in the Files Directories, some BBS
    automatically advise on what's new  at  time  of  initial  Logon.   Some
    Sysops  have the mistaken notion that running a BBS can be a neat way to
    accumulate a lot of  good  software.   It  really  works  in  the  other
    direction.  A good Sysop will have access to files long before his local
    users will. He quickly realizes it's he who will ALWAYS be providing the
    latest  stuff and not his users. For this reason I suggest steering away
    from any Boards that demand certain Upload/Down load  ratios  (what  you
    contribute vrs what you take). In any case, most contributors cause more
    problems  than  they cure. They will repackage (re archive or compress a
    file under an altered name) in order  to  re  transmit  it  for  credit.
    Sometimes  they  leave  important  things  out that could be grounds for
    license violations of the software.  Then  there  is  the  Virus  thing.
    Although  at  this  point  I  see  NO  PROBLEMS AT ALL in this area, the
    potential is there. Perhaps for curiosity sake a few  definitions  might
    be  in  order.  There  are usually three adjectives tossed about; Virus,
    Worm & Trojan.  Each has  a  separate  but  similar  meaning  with  some
    crossover  effects.  Basically,  a  Virus  is  a segment of code that is
    capable of altering your operating system file (usually COMMAND.COM)  in
    such  a  way as to cause the virus code to be written into any files you
    transfer to floppy either via the operating  system  or  the  executable
    files  themselves.  This  replicates the code (like a virus multiplying)
    onto  disks  that  may  ultimately  infect  other  machines.   The  code
    theoretically  could  be  constructed  to remain dormant until a certain
    system date comes up or after the machine is booted so many times.  Then
    it could pop its ugly head and cause all kinds of trouble. Possibilities
    are  a reformat of your hard drives, a crippling slowing down of the CPU
    clock cycle, altering Interrupt vectors causing system crashes,  locking
    the  CPU  into a constant reboot cycle....the list is endless. A Worm is
    identical to a Virus in damage possibilities but its not intended to  be
    passed  on  or  replicate  itself.  A  Trojan on the other hand is in my
    opinion the worst possible threat. This is a program that  sells  itself
    as  a  game or utility while in fact is purely intended to cause harm to
    your system. Why is it so dangerous as compared to a Virus or Worm ?  It
    has  to  do  with  Intelligence  itself.   The  kind  of  PhD education,
    experience and training it would take to write  an  effective  Virus  or
    Worm  generally  would  ethically  and morally preclude the creator from
    doing it in the first place. He would in reality have to be off  balance
    and  suffering  severe mental and emotional distress to conceive of this
    as punishment or payback. In any case there are perhaps less than a  few
    dozen  minds  in  the country who are even capable. BUT, the Trojan is a
    different story. First, almost any college educated hobbyist could,  via
    the readily available high speed modern compilers available today in any
    software  store,  write  a  simple  trojan that starts by playing music,
    let's say, while using that  to  mask  the  sound  of  your  hard  drive
    reformatting.  It would not take much creativity to come up with an idea
    and write the code for it. Anyone familiar with Pascal or "C"  could  do
    it.  For  that matter it could be done in BASIC. Well, "What can be done
    ?" you ask. Actually a lot if you are willing to take the effort. Keep a
    virgin copy of COMMAND.COM locked away on a diskette with a  known  good
    copy  of  the  two operating system files. Use a CRC checking Utility to
    determine the CRC value of the original copies,  including  their  exact
    byte length. The man who could alter a file, imbed a Virus, and do it in
    such  a  way  as  not to effect the CRC and byte length of the file just
    doesn't exist because that'd almost impossible. (yea, I did say almost).
    Also, just as every criminal act must have a  motive,  no  hacker  would
    take  the time unless he could get some kind of ego trip going.  Once he
    bit your hand it would be meaningless unless he got to inform  you  that
    you  were  a  sucker  and  taken !. To do this he would probably have an
    ASCII message in the code to  that  effect.  There  are  many  utilities
    capable  of  scanning an executable file for hidden messages.  There are
    also a number of utilities that are  capable  of  searching  through  an
    executable  file  for  calls  to  certain  DOS  Interrupts that would be
    necessary to play havoc with  the  central  processor  or  mass  storage
    devices  (hard drives, tapes, etc). Right now, in my opinion, this whole
    business of Virus etc. is more a question of knowledge  and  preparation
    rather  than  fear  and  reality.  Cuba could send a strike force up the
    Mississippi to invade the US via New Orleans. There are even  occasional
    reports of vessels at the mouth of the river. What does reason and logic
    say  about  this  ?.   One  real  tragedy  of human nature involved with
    personal computers is the user who either unknowingly or  while  engaged
    in  experimentation  trashes  his  hard  drive or corrupts his files and
    rather than accept personal responsibility claims foul Viruses  did  him
    in.  Sort  of  like a modern version of "Crying Wolf".  Its been done so
    often, will we believe it if it ever actually does begin to happen ?

    Now lets talk about archived files. An archived file is  rather  like  a
    file  box.  A  repository  or  collection of a number of separate files,
    organized or indexed in such a matter as to  make  retrieval  quick  and
    easy.  There is one special difference however. The files are compressed
    to their minimum possible size before being stored in the archive.  This
    compression  technique  can be based on a number of either compatible or
    no compatible methods. The first clue is the extension on a  file.  Here
    are  several  very common ones: .ARC, .PAK, .ZIP, .LIB, .ZOO.  Generally
    these are not compatible methods  and  each  requires  its  own  special
    utility  (work  program)  to  compress  and  un-compress.  There is even
    another method called suitcase files which have an ordinary extension of
    .EXE, but when executed immediately begin spawning many additional files
    that  come  from  within  the  main  suitcase  file  itself.   They  are
    automatically  uncompressed  as  they  are  re  written  back to disk by
    instruction or programming from within the  suitcase.  Since  they  look
    like  any  other  executable  file  it  is  sometimes  difficult for the
    inexperienced to tell them apart as being suitcase  files.  There  is  a
    trend  developing,  due mostly to the influence of BBS's, to standardize
    the algorithm's (formulas) used to archive. There  is  to  this  day  no
    clear cut winner. However, ZIP files (for being Zippered up) are showing
    up everywhere, perhaps becoming the dominate method. Time will tell.  In
    the  meanwhile,  it  can't hurt to begin collecting the top four or five
    Compression utilities. Then, no matter what you encounter, you  will  be
    prepared. Most all good BBS's carry them all in the Archive/ Compression
    directory  of  their  Files  department. Aside from going with the flow,
    things to consider if you have a lot of personal use for  storing  files
    are:  The  speed of both compressing and un-compressing, (remember, time
    is money); the degree or % of compression (how much space are you really
    saving); ease of use; extra utilities (i.e.   the  ability  to  password
    protect,  etc  etc);  registration  cost;  support  if  you need it; and
    suit-caseing ability. I fine features I like  in  each  of  the  popular
    methods but again due to BBS impact, find myself working most often with
    Zippered files.

    Now  its  time  to  talk  about  how to get the files to your end of the
    computer, (downloading), then we will discuss  the  opposite  situation,
    contributing  a  file  to someone elses system (uploading). As with most
    situations there is sort of a convention of thought when it comes to the
    keys used to manipulate a communications program.   Normally,  PgUp  and
    PgDn  bring the upload or download menu into view. Lets start first with
    downloading. Assuming you found your way into the Files section of a BBS
    and had opportunity to request a display of all (N)ew files  since  your
    last  time on (or perhaps used the BBS searching utility to determine if
    what you want is present) your next step is  to  request  a  (D)ownload.
    Some BBS require that you be within the specific file directory that the
    file  is  located  before  starting, some will allow a download from any
    location within the files section. As soon as you  request  a  download,
    the  BBS  will  usually  first  as  for  the desired protocol (method of
    sending the file which must be the same on both ends).   Some  BBS  have
    your  preference  protocol  as  a  default. (a protocol you requested on
    initial registration). Then, the name of the file is requested.  If  you
    type  it  in wrong or its really not there, the BBS usually informs you.
    Otherwise you get a message to continue on your  end.   YOU  DON'T  have
    all-day,  usually  60  seconds.  Here is where you hit PgDn on your end.
    Depending on the protocol selected you may or may not have to retype the
    file name on your end BUT you must pick the EXACT  same  protocol.  From
    here  on  the  process  is rather automatic and you can usually go about
    some other duties in the room until it beeps that its finished. The file
    will either be deposited into your default  directory  or  if  the  comm
    program  allows,  wherever  you  instructed  it  to  go. Lets talk about
    protocols for a moment. The common one are  Ascii,  Xmodem,  Ymodem  and
    Zmodem.   Most  everything  else  is  variations of these such as Clink,
    Mlink, Jmodem, Lynx, etc  etc.   Its  true  that  a  few  protocols  are
    inter-compatable  but  if  you go by the rule of sameness for BOTH ends,
    you can't go wrong. Some  protocols  allow  the  selection  of  multiple
    filename's  for  transfer  such  as  Ymodem/Batch  and  Zmodem.   My own
    preference is Ymodem/Zmodem when available. Zmodem has a few intelligent
    features that under some trying circumstances could be handy. It has the
    ability to reduce or  increase  packet  size  depending  on  quality  of
    transmission  conditions. It also has a crash recovery mode. Meaning, if
    you lost connection halfway through a file transfer, you could reconnect
    and pick up where you left off (without repeating the entire file).   On
    the  other  side  of  the coin there are still a large number of systems
    using only Xmodem and Kermit. Kermit is a protocol used when a  personal
    computer  has  to  exchange  data with a big main frame. Its seldom ever
    used PC to PC. Because of computer design, storage design  etc.   packet
    sizes  can  vary  from  128  bytes  of  data  too several k. Sizes of 1k
    (1024bytes) are the more common. The only real reason for limiting  size
    is  quality  of  transmission  medium.  If a transmission medium is 100%
    capable, there really be no  need  to  limit  packet  sizes.   On  clean
    systems,  Jmodem  is  popular  because  of  its  ability to run up to 8k
    packets. This saves a small amount of time but in my opinion  not  worth
    the risk of some corrupted bytes getting through. (a byte whos value has
    been altered from its original value by a change in one or more of its 8
    bits)

    If you desire, you can obtain services on Telephone Network systems that
    are on the average much cheeper than regular long distance services.  US
    Sprint  has a Telenet System that only cost $1.00 per your for the first
    30 hours of time. Yes, there are a few hooks. You pay 30  buck  a  month
    regardless  of  the  minimum  used and are limited to perhaps only 40 or
    less cities. Still, considering AT&T at  $6+  per  hour  this  can  save
    money.  Slick has a special set of built in Macros to make logging on to
    Telenets PcPursuit service an easy process.

    Lets talk now about some simple rules of  BBS  etiquette.  First,  never
    drop carrier (hang up) when you are finished. Take the time to leave via
    the  proper exit (Goodby or Off key). Dropping carrier is the equivalent
    of having a guest suddenly leave your home and SLAM the door on the  way
    out.  Second, dont POST (leave messages) in ALL Capitol Letters. This is
    the equivalent to shouting in someone's face. Third, if you are going to
    use someone's else's BBS, operate according to his rules. If  you  don't
    like  the  rules,  go  some-where  else where the rules are more to your
    liking.  Finally, be cautious. If you are intent on pranks you should be
    aware that most ALL forms of communication are supervised and  protected
    by  federal laws. Its easy to get caught when on a phone system today as
    everything is a matter of record.  With  ESS  offices,  the  system  can
    log/trace anything, anytime it's necessary.

                                     EOF