own comprehensive and successful standards in
computer networking.
The operating system enables a computer to do
several tasks at the same time. A particularly
important development was timesharing. The
Computer Time-Sharing System – CTSS – was
demonstrated in its earliest form at MIT in the
early to mid 1960s. Timesharing permits several
users to access the computer simultaneously.
Several user terminals, typically Teletype
machines, may be connected to the computer.
Each user experiences the communication with
the computer – via the timeshared operating sys-
tem – as if she had the computer to herself alone.
The computer actually shares its time between
several users and several tasks. The users per-
ceive increased load from more users as slower
response from the computer. Powerful comput-
ers may serve many, perhaps several tens of
users without noticeably slow response.
Standard Teletype machines are specialized
typewriting machines made to be connected for
transfer of written – teletype – messages through
the international Telexnetwork. In the 1960s
specialized typewriting computer terminals
began to replace the use of Teletype machines
for computer purposes. They were faster and
more flexible to use, had more comprehensive
character sets and could produce nicer print.
Only from the beginning of the 1970s terminals
with Cathode Ray Terminal screens became
more and more usual. From around 1980 CRTs
were dominating computer use. Terminals are
connected to computers via [telephone] lines.
Gradually it became usual to employ the tele-
phone network for communication with comput-
ers. The signals between the terminal and the
computer were converted into signals that could
be transmitted similarly to speech signals. They
were “modulated” and “demodulated” by
modems. In this way users of computers could
have terminals placed at the users’ premises,
connected to computers elsewhere via fixed –
leased – or “dial-up” telephone lines.
Vendors of computing services established large
computer centres sometimes with extensive nets
of leased lines and connection points for modem
connections. The one single application making
most use of early computer networking was seat
reservation for airline passenger traffic. Already
in the 1960s the large airlines had ubiquitous,
often global networks for that purpose.
Computer Centres and
Personal Computers
For economic management of expensive com-
puters stable full employment of the machine is
important. Before the invention of timesharing
computer centres were run in “closed shop
mode”. The actual users, i.e. those who devel-
oped programs and those who delivered data for
processing, were not allowed to communicate
directly with the computer. The user submitted
jobs consisting of programs and/or data, usually
in the form of a deck of punched cards or a roll
of punched paper tape. A popular profession was
that of punching machine operator, transferring
written programs or data from paper into
punched cards, using the specialized “off-line”Special printer terminals
became availableThe line printer was the output
medium from computer
centers. It produced large
amounts of printed pages
folded together