# Introduction to Internet

If you are (or want to be) new Internet user, and Arachne is your first encounter with technical terms describing Internet protocols and applications and their configuration, configuring Arachne will not be easy task for you. This page contains short explanations of the most frequently used words in Arachne documentation.

### Internet

Internet is the worldwide network of computers, based on TCP/IP protcol. It allows you to use many different services based on various Internet protocols. Internet is also known as "Information highway".

Most popular services are WWW and eMail, based on protcols called HTTP, SMTP and POP3. Other well known services are FTP, Usenet (news - protocol NNTP), Telnet and IRC. If you don't understand what words like "service" or "protocol" mean, just picture all this stuff as alternative or enhancment to well known electronical communication services like televison, voice phone or fax.

There are also another experimental services, like Internet Phone, See-You-See-Me, PointCast network, ICQ or Internet Radio, which are not generaly understood as Internet standard. Some of Internet protocols are rather historical, like Gopher or Finger. History of Internet is very interesting chapter, if you are interested in it, try to get some book about Internet.

### TCP/IP

Family of communication protocols used on Internet. Something like engine in a car: users don't have to know how it works, they have only to know which kind of fuel they need, and where to go, if something goes wrong.

Most important among TCP/IP protocols are TCP (transmission control protocol),IP (internet protocol) and UDP (user datagram protocol). Pieces of data transported by TCP/IP are called packets.

Advanced operating systems (like Unix) implement TCP/IP as basic system service (on the same level as other I/O operations); in small systems like DOS, TCP/IP must be integrated to the application. This is why configuring Arachne is so confusing: you are configuring both TCP/IP and browser (and if you are using modem, than also a PPP dialer) in one program! You are provided with complete network solution, which together with operating system fits one floppy and can boot from it.

TCP/IP was designed for permanently connected computers; if you want to connect using phone line and modem, you will need to establish SLIP or PPP protocol between your Internet provider and your computer to transfer TCP/IP packets to your computer.

### WWW

WWW means World Wide Web. It's system of online hypertext pages, located on many servers all around world. Pages are written in HTML language and linked to each other. Pages can also contain links to objects of differend typs, like soundtracks, moovies, live audio and video broadcasting, etc.

Arachne is WWW client - program which can request, download and view HTML page. WWW uses protocol called HTTP.

Only mass communication technology as easy to use as World Wide Web is probably television. Users of world Wide Web are expected only to be able to read and to know how to use mouse to select hypertext links, nothing more.

### eMail

eMail, E-mail, or email are various shortcuts for "electronic mail".

Electronic mail is simply exchange of text messages (which can contain attached encoded files) between Internet users. Arachne can currently send and recieve simle eMail messages, using protocols called SMTP (sending eMails) and POP3 (downloading eMail from mailbox). Every user of internet mail is assigned unique address, in format username@domain. Your username does not have to be identical to your login name. The domain is ussualy (but not always) a name of your provider's mail server.

Having personal eMail address is today probably as common, as having personal phone number.

### PPP

Point to Point Protocol. Protocol which transfers TCP/IP packets through your modem and connects your computer to Internet. There are three ways to authenticate PPP connection: First option is to ask for manual login (like if you are calling BBS system) and then PPP protocol starts without further verification (in terminal window you will see bunch of characters like ~,#,!, etc.). Arachne can automaticaly login to such provider, if you configure it correctly. Second option is called Password Authentication Protocol (PAP) and the third one is Challenge Authentication Protocol (CHAP). PPP dialers shipped with Arachne currently supports PAP, but CHAP is already supported by latest release of DOSPPPD.

### URL

Universal resource locator. You have probably seen announcments like "Visit internet hompege of Some Company at http://www.somecomepany.com/. This is typical URL. It is identifier for resource accesible by WWW browser, most often a HTML page accessible using HTTP protocol. In Arachne, you must first connect to Internet. Once you are connected, just press F3 key, enter the URL you want to surf and press Enter.

The URL syntax is protocol://[username[:password]@]hostname[:port][/URI]

URI is shortcut for Uniform Resource Identifier, and it is in fact very often just a filename of document or program located on WWW server.

### OpenDOS

We described Arachne as "DOS application". It means, that basically, Arachne can run under various types of MS-DOS 3.3 compatible operating systems: MS-DOS up to 6.22, Windows 95, OS/2, DR-DOS, NovellDOS, DOSEMU under Linux, SoftPC under NextStep (all these options were tested). However, we recommend you to use Caldera OpenDOS, clone of DOS, which is free for non-commercial use. Even unexperienced users can easily configure OpenDOS using built-in setup utility. And you can easily download latest patches and upgrades of OpenDOS from Caldera Website.

OpenDOS is latest member of Digital Researh's CP/M development line: CP/M ... CP/M ... DR-DOS ... Novell DOS ... Caldera (DR)OpenDOS.

### DOS memory

When you are using MS-DOS, your computer starts in "real mode" of your Intel compatible processor: it means that even if you have Pentium, your computer generally behaves like PC XT when you boot DOS. It means, that only 1 MB of RAM can be used directly by your programs, and the largest executable program size can be up to 640 kB (but ussually less, as there must be also various device drivers present in a memory). More memory than 1 MB can be accesed only as storage space for data, called XMS or EMS memory.

But you are likely to have 386 or better processor, which can be switched to "protected mode" (also called "32bit" mode) and access all memory. From DOS, you can do this for example by using DPMI driver. You are probably asking, why Arachne is real mode application, running only in the first 640 kB of your PC's memory: it's because golden era of DOS was on real mode computers and most development tools, libraries and helper applications feel best in real or "V8086" (also called "Virtual") mode of processor. Developing for protected mode DOS is much more complicated task.

Arachne, as real mode application, is very small program, which fits on single floppy: compare this to protected mode applications, written in object-oriented languages, which are ten times bigger and you are downloading them from Internet for ages. Arachne was developed mainly for PCs with 80286, 80386 or 80486 compatible CPU, with only several MB of RAM, where real mode DOS applications perform much better than Windows applications. On Pentium P5/P6 (trademark of Intel), AMD K5/K6 or various 80586 and 80686 compatible machines with more than 8 MB of memory, real mode applications are not able to use the full potential of the system. However, you can use extended memory manager like EMM386 or QEMM to optimize "virtual DOS machine" on your 386 or better computer to be very efficient and actually much faster then operating system which are expected to run on these machines. Using DOS on Pentium class computers can give you probably more "real-time" feeling then using any other OS.

### RAM disk

DOS is able to use extra memory of your system as virtual file system, called RAM disk. If your PC have more than 8 MB of memory, you should definitely think about cofiguring such RAM disk to increase speed of your DOS applications, including Arachne. This will give you probably the fastest operating system ever available: while 32bit operating systems use your hard disk as virtual memory, with 16bit DOS you can use your memory as very fast hard disk. This can increase for example speed of JPEG decompression in Arachne, etc. The problem is, that content of RAM disk is lost when you turn your computer off. Configuring Arachne to run from RAM disk (by copying it's home directory to RAM disk) but to use directories on hard disk for mail and downloaded files can be good solution.

Check your system manual or configuration utility for information how to configure RAM disk on your PC.

This list will be more complex in the future releases of Arachne