Nepedia
Back to Discover
Advanced Reader
💻

Time-sharing

technology Maturity 9-11 Next article →

Time-sharing is a method in computing where a single resource is shared among many tasks or users. It works by giving each task or user a very small slice of processing time. The computer switches between these tasks so rapidly that it creates an illusion. To the user, it feels as if the computer is executing all tasks simultaneously. This technology enables multitasking for one person or allows many people to use one machine at once.

Unix Timesharing UW-Madison 1978
Unix Timesharing UW-Madison 1978

By allowing concurrent interaction, time-sharing dramatically lowered the cost of computing. It meant people and organizations could use powerful computers without needing to own one.

Before time-sharing, computers used a method called batch processing. Early computers were extremely expensive and very slow. Operators had to manually enter programs using control panels and switches. These programs often took hours to run. Later, batch operating systems like IBSYS, released in 1960, helped by queuing programs to reduce "dead periods."

Even then, the process was slow. Programmers wrote code "offline" on paper tape or cards. They then gave these to an operations team to schedule. A programmer might wait days to receive their printed output. This made interactive development very difficult and expensive for most people.

The concept of sharing computing power evolved through several key ideas. In 1949, Robert Dodds described a form of multiprogramming in a letter. In 1954, John Backus discussed the concept at MIT. By 1957, Bob Bemer suggested that computers could act like a utility. He imagined providing computing power to many users just like electricity companies provide power.

Unix Timesharing UW-Madison 1978
Unix Timesharing UW-Madison 1978

In 1958, W. F. Bauer described "parallel systems" that allowed large components to be shared. Christopher Strachey then filed a patent for time-sharing in the United Kingdom in 1959. His paper in Paris was later credited as the first paper on time-shared computers.

After 1960, the meaning of time-sharing shifted toward interactive use. The Compatible Time-Sharing System, or CTSS, was a major milestone. John McCarthy initiated the idea at MIT in 1959. Fernando J. Corbató led the development of the system. A prototype was tested by November 1961.

IBM supported this work by loaning mainframes like the IBM 704 and 709 series to MIT. There were specific rules for this loan. MIT could not charge for CTSS use. They could only use the machines for eight hours a day. Another eight hours were reserved for other colleges. IBM used the machines for the remaining eight hours.

Other important systems emerged during this era of discovery. The BBN Time-Sharing System began operation and was demonstrated in 1962. JOSS started its service in January 1964. The Dartmouth Time-Sharing System, or DTSS, began in March 1964. DTSS was quite efficient at handling many people. It supported more than 100 simultaneous users. While some jobs took ten seconds or more, 78% of jobs needed one second or less. About 75% of its 3,197 users used their terminals for 30 minutes or less. These numbers show how effectively the system managed its resources.

In the 1960s and 1970s, many companies became service bureaus. They provided time-sharing as a professional business. Users connected via modems that moved characters at speeds between 10 and 120 per second. They were charged for terminal rent, connection time, CPU time, and disk storage.

Unix Timesharing UW-Madison 1978
Unix Timesharing UW-Madison 1978

Common systems included the PDP-10 and the IBM 360. By 1968, thirty-two service bureaus served the U.S. National Institutes of Health alone. By 1975, Prime Computer's president noted that time-sharing was the biggest end-user market. This era saw many companies like Tymshare and National CSS thrive.

The rise of the personal computer changed the industry. In the early 1980s, microprocessors became cheap enough for individuals to own. A single person could have all the CPU time for themselves. This caused the traditional time-sharing business to decline. However, the core concept has returned through the Internet. Today, expensive server farms host thousands of customers. These servers share common resources among many users at once. Web sites operate in bursts of activity, much like the old systems. This allows modern computing to remain efficient and highly accessible.

693 words

Where will your curiosity go next?

Keep exploring at your chosen reading level.

🖼️ Images & Media (1)
File:Unix Timesharing UW-Madison 1978.jpeg
Unix Timesharing UW-Madison 1978.jpeg
More to explore

What is Nepedia?

A free, ad-free encyclopedia for children. Every article is written at five reading levels, so the same page works for a five-year-old and a fifteen-year-old — use the level switcher above to see this one change. No account needed to read.