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information can be transported through different

types of transport media. Each transport is auto-

matically handled as required by interconnected

carrier media that may have different character-

istics.

The transport is handled according to technical

rules called protocols. They depend on more

detail and are significantly more complicated

than the protocol that govern ordinary telephone

traffic. In reality the protocols are implemented

as programs in computers. Microprocessors of

various processing powers are now available and

can be used as components in devices built to

use the Internet for various purposes. It appears

that we are presently at the beginning of an era

of future types of information networks.

Remote Computers and

Time Sharing

Early computers and their users communicated

using teleprinters – “Teletype machines” – that

conveyed text directly both into and out of the

computers. For many years information was

transferred in and out of computers via punched

cards or punched paper tape. The need for effi-

cient use of computer time dictated these media.

They were much faster and hence occupied less

of the valuable computer time waiting for slow

fingers and printer mechanisms. Special line

printers to be directly driven by the computer

were developed. For many years powerful line-

printer machines were essential parts of com-

puter centres, and they produced vast amounts

of paper printouts. Although they are capable of

fast printing of text on paper lineprinters have

been surpassed in performance by newer de-

vices. Both ink jet printers and xerographic

printing mechanisms using lasers for pattern

generation are almost household items today,

and they outperform the earlier, powerful mech-

anical line printers both at efficiency, quality and

flexibility.

The first operating systems were developed early

in the 1960s. That is programs that manage the

computer itself and its attached resources. Since

then a computer without an operating system is

unthinkable. The operating system manages the

computer and its various tasks. As an example

the operating system permits the fast central

processing unit to carry on at full speed while

slower attached units such as printers work at

theirspeed. Important operating systems today

are Windows, NT, UNIX and Linux, each in

several variations. While Internet-technology is

independent of individual machines and operat-

ing systems, the one operating system that was

most prevalent during the first decade of net-

working development was “Tenex” by Digital

Equipment Corporation – DEC. It was a popular

operating system especially for that company’s

tenth major computer model (“Programmed

Data Processor”) – PDP 10. Towards the end of

the 1970s Unix became more and more popular

and has become an important industry standard

serving many types of computers. In the 1990s

Microsoft Corporation’s various “Windows”

systems have overtaken it in volume outnumber-

ing all others.

A remarkable phenomenon during the period

of internetworking development is the absence

of IBM from that development. From the late

1950s that large, internationally distributed com-

pany had a uniquely large market share for com-

puters and everything in computing. Especially

IBM took leadership in many areas of technical

standard setting. Cards, magnetic tapes, codes,

etc. were “IBM-compatible”. IBM also set their

• • • • • • • •

Tele-net

Modems

Terminals

Modems

Computer

center

Timesharing allows many
users to work directly and
simultaneously with the com-
puter from remote locations

Figure 5 CRT-screens and
timesharing were major steps
in adapting the power of
computers to the abilities of
people. This picture was copied
from a brochure in 1971. The
large company impressed
customers calling in. As soon
as the customer gave his name
the operator could (actually
type it immediately and thus
display his data, hence –)
“remember” details about him