Mosaic for Beginners

[Ray Harder <rharder@EIS.CALSTATE.EDU>]

Here are a few comments that can help you all to understand not only that you
can or cannot run Mosaic, but more importantly *why.* These comments are
designed for beginners and neophytes with some telecommunication experience,
but not much. It is from a rough draft of some things I am writing so please
credit me and let me know if you use it elsewhere! I haven't even reached the
spell checking stage yet, so please don't embarrass me with it! Comments and
corrections are welcome. This first part talks about the concepts behind
Mosaic. The second will tell about what it takes to get Mosaic working.

Part 1: What is Mosaic?

Mosaic is a Hypermedia Browser for the Internet. (Huh?) What that means is that
it is a piece of software that allows you to bring up a "Page" or screen of
information. This screen might have text and pictures mixed together on the
same screen in much the same fashion as a magazine or newspaper. However, this
is where the similarity ends. On a computer, the Hypermedia page can include
not only pictures and text --like traditional paper-based publications, but
also sounds or videos that are a mouseclick or return key away. However,
Computer based Hypermedia doesn't stop there. On a Mosaic page you can bring up
a screen that has three dimensional, manipulable objects which can be turned or
rotated with the mouse or arrow keys; or have a screen that allows you to type
a keyword and have the Mosaic deliver this in the form of a request to another
computer far across the Internet. That computer might have on it the complete
text of all of the speeches, letters, papers, press releases, and comments of
the Clinton administration. (Maybe even the texts of all shredded documents...
Well, it *could* happen ;-)> That computer would then search all of these
documents and see if any of them match your search word (Let's say "Somalia").
The computer would send back a list of files from the Clinton administration
which related to the subject requested. Your copy of Mosaic shows this list of
files on your computer screen. When you click on one, Mosaic gets that file
from that far away computer and brings it to your computer.

Wait a minute. If Mosaic can allow you to use another computer far across the
Internet without learning all about it, what else can it do? Let's back up.
Usually, when we think of computer based Hypermedia, we think of putting a
whole bunch of text, pictures, sounds, movies, animations, etc. onto a giant
hard drive and opening that information with our software HyperMedia program
like HyperCard, HyperStudio, Linkway, or whatever. The Hypermedia program has
an instruction that says in computerese: "There is a text file on the hard
drive called MYHARDDISK and on that disk, there is a folder or directory called
TEXTFILES, and in that directory there is a file called ABOUTMONKEYS. Open that
file and put the words on the screen right here in this little box." The
computer repeats that same process to get the picture of the monkey from the
PICTUREFILES directory and places it next to the text that was just retrieved.
Ok, simple enough (You call this simple? You must think that The Terminator was
a movie about networking!), but what does this have to do with Mosaic etc? I'm
getting to that, hang on to your mouse!

Most of you are familiar with the concept of a network file server. What this
means is connecting one or more computers to another computer and using its
hard drive (At least this is one function of a network). We could create a
Hypermedia document about Monkeys where the text and picture files are on the
hard drive across the room instead of inside our computer, right? This is a
Local Area Network or LAN. Most of us have opened up pictures that are
physically across the room or across campus on a file server.  This helps us to
understand the idea of retrieving files from far away. OK, so we could put our
Hypermedia stack together that retrieves files from a hard drive other than the
one in our computer.

You could also set up that file server across town or even halfway across the
world. This would give you a Wide Area Network or WAN. The Internet is
essentially a giant distributed network with all kinds of file servers with all
different types of capabilities and contents. Why couldn't we set up a
HyperMedia program that had buttons that you could click and it would say in
computerese: "Go across the Internet and find a hard disk called
THE.BIG.HD.AT.XYZU on this disk there is a directory/folder called
ALL.ABOUT.MONKEYS and in there you will find a file called CHIMPS. Go get that
file and bring it across the Internet and put it in this little box here."

This is essentially what Mosaic does. If you look under the hood, Mosaic uses
rather simple little files in plain text (Know as ASCII, or unformatted text).
These text files are instructions in a computer language called HTML. It is
really a language that describes a computer screen. It says things like "Put a
picture here or a text there on the screen." It also has some other neat
features like, "When someone clicks here, go across the net, get the sound or
video file that is pointed to and bring it back to my machine and play it."
Mosaic is technically what is called, in Geek, a Parser (at least that is it's
major function, it's a hybrid and pretty hard to pigeonhole!). It takes
instructions in HTML language, which is semi-readable by certain nerdy human
types, and translates it into ones and zeros (Machine language) which is the
only language computer chips understand.

So, Mosaic is a computer program that creates computer screens that are
composed of text, picture, audio, video, animation, and other types that are
pulled from anywhere on the Internet and "played" on your computer (So why
didn't you just say that at the beginning?). Another nice feature of Mosaic is
that the text might be coming from a file server in Australia while the picture
on your screen at the same time might have come from the Netherlands.

OK, since Mosaic will make every other discovery of mankind seem like raw
toast, can I run it from home or not? See part two of the continuing saga in
the next part....

------
Part 2
------

I've heard that I can't run Mosaic from home is that true? Why?

Mosaic is a program that runs on a computer which is directly connected to the
Internet. Since Mosaic is a computer program, it is machine specific. Or more
simply, you have to have a version of the program for your particular machine
(A Windows version, a Unix version, a Macintosh version, or whatever.). This is
so that Mosaic can talk to your machine. But remember, Mosaic is a kind of
techno-translator. It acts as a go between to get your computer to talk to
other computers on the Internet. So what language do Internet computers speak
to each other? Remember the Internet is a network of networks. Your machine at
work is probably on some kind of a network. The computers on the network talk
to each other in some form of net language. These languages are different for
Apple Networks, Novell, Token Ring, Windows NT, etc. If there are thousands of
little networks connected together as the Internet, which of all of these
languages do they speak to each other?

Computers on the Internet speak TCP/IP. This is universal "Internetese." TCP/IP
is the Esperanto of the Internet. Perhaps the simplest definition of the
Internet is: all the computers in the world that talk TCP/IP to each other.
(There are of course TCP/IP networks that are not connected to the Internet.)
Each computer on the Internet has to have the software installed to be able to
translate from its programs so that those programs can talk across the
Internet. Mosaic needs to have a clear channel between it and all of the other
computers on the net. This channel must have computers all along the way that
can talk TCP/IP. So, I can use Mosaic if my computer is on a network that
speaks TCP/IP. What language am I speaking when I dial into the Internet from
home with my modem?

Normally, when dialing into a network from anywhere, you are using a modem to
turn your phone lines into a kind of a network wire. Since computers (which are
digital --they speak ones and zeros) don't speak telephone (which are analog
--they speak waves) you need a modem to change the waves into high waves and
low waves. In effect this makes the phone lines able to send ones and zeros by
making a high wave a one and a low wave equal a zero. This process of
converting each signal, sending it, and converting it back at the other end, is
cumbersome resulting in a pretty slow network. Also, this kind of setup
requires that the signals be sent one after another in a line or serially.
(Hence the name of the port to which your modem is connected --the serial port.
This is unrelated to the Cereal port which is where Cornflakes come out of your
computer. Just seeing if you were paying attention!) OK, if phone lines can
send the equivalent of ones and zeros, then why can't I run Mosaic across them?
Well, theoretically, you could. However, most dial up connections are speaking
to other computers as if they were just dumb terminals using a language like
VT100 or something.

What is VT100? Well, this goes back to the old days of computing when The
Computer was this monster machine down the hall in The Data Processing
department maintained by a bunch of guys with masking tape holding their
glasses together and wearing pocket protectors. What you had on your desk was
not a computer, but a terminal. This is a fancy way of saying that you had a
monitor and keyboard with long wires attached to the computer itself at the
other end of the building. You had no computing power on your desk, just a
Video Terminal. This Video Terminal or VT had to get certain signals from the
computer that where known and fixed so that it knew whenever the computer send
these particular signals, to put this or that character on the screen etc. One
of the languages that terminals communicated in was VT100 (Others were VT102,
VT52, ANSI BBS, etc....). These languages were basically designed to allow your
monitor and keyboard to operate another computer far away. They were never
designed or intended for sending anything sophisticated like network signals.

When you are dialing into a computer, you are usually just using your computer
as a dumb terminal (You mean I spent two months pay to buy a fancy monitor and
keyboard and then had to buy a modem to get it to work? And, it's not even
acting like a computer? Yep, that's about the size of it!) With this
arrangement, you are just using your keyboard to operate software that is on
the computer you are dialing up. If this computer is on the Internet, then you
can get it to talk to the Internet for you, but your computer is not talking on
the Internet itself. If the computer you are dialing has Telnet software or
Gopher software or FTP software on it then you can get it to go out across the
Internet and use these tools for you. Gopher and Telnet are text based by their
nature and they send the character based screens to your screen via the VT100
serial connection. This is relatively transparent and there isn't much
difference between dial up and full Internet connections. FTP is a different
story. FTP software is the Internet's way of copying files from one Internet
computer to another. Like Mosaic, FTP software needs to speak TCP/IP to the
computer it is retrieving the file from. This is why when you are dialing up
the Internet you can FTP a file from a far away computer to the one you are
dialing up, but you can't FTP from the far computer to your home machine
directly nor can you FTP from the one you are dialing to your home machine
after transferring it that far distance to the one you are dialing into. After
an FTP (which moves a file from one TCP/IP connected computer to another), you
then need to change over to your local software and transfer the file from the
dialup computer to your local machine using a language like Kermit, or XModem,
or YModem, or ZModem. These are languages (Or in proper Geek: Protocols) which
were designed specifically for the time when microcomputers began to be used in
place of video terminals. This was a time when you not only needed to look at
screens from the computer down the hall on your terminal, but since your
terminal was now a real computer, you sometimes wanted to get a file from the
big computer and do something with it on your machine. Since VT100, ANSI BBS,
etc. didn't allow file transfers, then new methods and languages were developed
that would.

Since connections between terminals and mainframes were serial, dialup
connections acted the same way. But now in the world of the Internet, we want
to actually create a network connection. We want to run Mosaic, Turbo Gopher,
Fetch, Cello, etc. on our own machines and not have to use another computer as
an intermediary. In short, we want to be able to speak TCP/IP across a phone
line. Is this possible?

Well, those geeks in Cyberspace have come up with a bit of technomagic that
allows computers to dial into the Internet and speak TCP/IP. It is called SLIP
(Serial Link Internet Protocol). This allows computers on a dialup line to act
as full Internet participants. They can speak TCP/IP, they have their own
Internet addresses, they can run Internet software --including Mosaic! Okay, so
how does it work? Can I just add SLIP software to my computer and dial up in
the usual manner? Well, unfortunately, it is not quite that easy.

SLIP requires special connections at the receiving end as well. You can use
your same computer, modem, and phone line, but you cannot dial into an ordinary
modem bank like you have been using. You need to dial into a special connection
called a SLIP server. Your site may or may not support this. In addition,
whoever runs the system you are dialing into must add your name and password to
their SLIP server database. If your connection provider can give you this, then
you can add SLIP software to your PC. The SLIP software needs to be used
together with TCP software to make your computer a full Internet participant.
Once these tools are installed properly, you can dial into the Internet and use
Mosaic, Fetch, Gopher, Cello or any other Internet software that you can find
for your PC. But, be warned, the fastest modem does not reach anything like the
slowest network connection speeds. You can expect transfers of about 3 MB per
hour from a 14,400 baud modem. This means that an audio file of someone reading
aloud a moderate sized poem, like Edgar Allen Poe's The Raven, will take over
an hour and a half to download!

Well, since that last paragraph reached the 14,000 character mark, I will take
that as an omen that it is time to quit! I do want to mention that SLIP is not
the only game in town. There are other serial connections that allow you to run
network pretending connections. Other connections that "fool" your computer
into thinking that it is on the Internet are PPP (Point to Point Protocol), and
ARA (Apple Remote Access). This latter works if you have an Apple Macintosh
network that is already Internet connected and you are dialing into a modem
connected to it. There are other solutions too. Talk to your network connection
provider and say, "I want my TCP/IP!"

This message was brought to you by Raymond G. Harder, educational technology
consultant and trainer, because it's raining in southern California and he had
nothing better to do today.

Ray



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* Raymond G. Harder                  "Can't walk today, I don't feel well."*
* Educational Technology Consultant  "Why don't you sit out in the sun?"   *
* 909-983-4713                       "What? People will think I'm lazy!"   *
* rharder@ctp.org                         -- My 92 year old grandmother    *
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