Computer "Time-Sharing" -- M.I.T

MIT Institute Archives & Special Collections. Massachusetts Institute of Technology. News Office (AC0069)

From the Office of Public Relations Massachusetts Institute of Technology Cambridge 39, Massachusetts Telephone: UN4-6900, ext. 2701-8 FOR IMMEDIATE RELEASE

Researchers at Massachusetts Institute of Technology are breaking a bottle neck

that has grown up around modern high-speed computers.

Using a new system of operation called "time-sharing" they are making it pos-

sible for many persons to use a giant computer simultaneously, instead of waiting in line or

leaving their programs to be processed by a machine operator.

Professor Philip M. Morse, Director of M.I.T.'s Computation Center, believes this new development will have enormous impact on the applications and methods of use of

computers. At present 5, and shortly 21, users can work problems on the Center's IBM 7090

at the same time, each user sitting at a separate control console, with which he directs the

computer's actions. Eventually more than 100 time-shared consoles, some of them in class-rooms, and some in laboratories, will be connected to a central computing facility.

Time-sharing is a way of making the capability of the big 7090 simultaneously available to a number of different users, operating from control centers which may be quite far removed from the central machine. Each user has at his disposal a device which permits instantaneous two-way communication with the computer so that the initial problem may be posed, intermediAte results obtained and examined, the problem restructured, if necessary, and run again without delay.

The new development has required a major reprogramming of the machine's

(more) Use copy created from Institute Archives record copy. © Massachusetts Institute of Technology MIT Institute Archives & Special Collections. Massachusetts Institute of Technology. News Office (AC0069)

2. Computer "Time-Sharing" -- M.I.T.

operation, says Professor Morse, so that the questions asked by one user will not interfere

with the tasks the machine is simultaneously doing for another user. Associate Professor

Fernando J. Corbato, the Computation Center's Associate Director, has been responsible

for the development of the new system,which already has required six to eight man-years of

programming work. Assistant Professor Herbert M. Teager has been in charge of design of

special equipment for the time-shared consoles.

Experience with the new mode of operation has convinced these experts that time-

sharing will make it possible to bring the electronic computer to the user -- the scientist

or engineer or business executive -- instead of requiring the user to go to the machine, as

is now the case. The new f lexibility of use will make possible many new applications in

theoretical and experimental science, they predict.

Engineers and scientists long have aspired to have complete and immediate access

to computers, an aspiration that has become increasingly difficult to achieve.

As computers have become larger and more expensive, pressures to keep the

computers busy have forced the adoption of operating policies and procedures which, while

improving over-all efficiency, have tended to impose a barrier between the individual user

and the machine.

In 1957, when the Computation Center at M. I. T. first installed an IBM 704, it was

believed that the computer would be so fast and so versatile that it would be able to meet all

the computation needs of the M. I. T. community.

Although it did satisfy the needs of a great many users, the demand for machine

3. Computer Time-Sharing -- M.I.T.

time soon resulted in an average delay in obtaining solutions of a day or more because of

the "batch-processing" system that had to be instituted to conserve machine time. Under

this, users submit problems -- in the form of decks of punched cards -- to a computer

staff which collects the problems in batches, transfers them to magnetic tape and feeds

them through the computer sequentially,

In an effort to reduce the delay between submission of a problem to the staff

and return of the answer to the user, the 704 was replaced by an IBM 709 in 1960. More

recently, the 709 was replaced by the even larger and faster 7090.

Yet, despite increasing machine size and speed, the demand for computation

service expanded just as rapidly. It is estimated that computation needs at M.I.T. and at

the 42 other New England colleges and universities served by the Center have just about

doubled every two years.

Equally important, batch service presents distinct disadvantages besides the

time delay. It makes experimentation with the computer difficult if not impossible. It

makes teaching of computer applications difficult because it permits neither teacher nor

student to operate the machine directly. In effect, batch service represents a barrier

between user and the machine.

These disadvantages contributed to the motivation for installation of smaller,

less versatile computation facilities within individual departments and research groups

at M.I.T. All told, there are now more than 20 digital computers on the M.I .T. campus.

Several departments also have extensive analog facilities.

But while access to these facilities overcame many of the disadvantages of

batch service on the larger machine, many programs and problems were too large to be

handled efficiently by these machines. A better approach was clearly required and it

soon appeared in the form of the time-sharing system.

Time-sharing a large computer depends not on its capacity to work many

problems at the same time, but upon its ability, made possible through new compilers

and executive routines, to concentrate intensively upon one problem for a very short

time (say, 0.02 second), then move on to the next problem, the next, and finally back

to the first in a round-robin fashion. Since the reaction time for the man at each console

is about 0.2 second, it appears to him that he has the full attention of the computer.

The computer's time-sharing ability is thus much like that of the man who reads

his mail while telephoning -- he is never doing two things at the same time, but rather

is alternating his attention rapidly from one to the other.

The M.I.T. time-sharing system presently has five electric typewriter-type

input-output consoles capable of simultaneous operation. Sixteen teleprinter-type consoles

located in various laboratories and offices soon will be linked to the 7090 computer via

telephone lines.

In addition, equipment has been installed to connect the Civil Engineering IBM

1620 and the Electrical Engineering PDP-l to the 7090. These smaller computers will serve

as powerful remote time-sharing consoles for the larger machine.

Eventually, the center researchers expect to be able to have more time-sharing

consoles of varied types capable of simultaneous operation. -- 30-- April 12, 1963 Use copy created from Institute Archives record copy. © Massachusetts Institute of Technology