Compatible Time-sharing System: An Overview of CTSS

Compatible time-sharing system
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Compatible Time-Sharing System (CTSS) is the time-sharing system that was innovated by the MIT Computation center during the period 1960s and 1970s The idea behind this innovation is the operating system can work on multiple threads. Time-sharing in CTSS means the system can perform multiple tasks at once. Here in this article, we will see an overview of the Compatible Time-Sharing System.

Time-Sharing Operating System

The method of operation in data processing where several users working with different programs can interact at the same time is the time-sharing operating system. To complete this operation, the user gets the help of the central processing unit (CPU) of the large-scale computer system. Time-sharing is developed to save data processing time and make efficient use of process time. This time-sharing technique includes the below-mentioned activities:

  • Multiprocessing
  • Parallel Operations
  • Multiprogramming
  • Exchanging data and resources

With the help of a time-sharing operating system, users can get access to a shared computer system through a central processing unit (CPU). For the users who are connected through a time-sharing system, there should be at least one program in the memory of this shared computer. The memory executes these programs in a short timeframe. This operating system is more complex as compared to others.

Importance of Time-Sharing Operating System

The time-sharing operating system is an important type of OS that enables users to operate a particular computer system from different locations. This system helps to reduce the processing time of OS by sharing among multiple users. The Importance of the time-sharing operating system is mentioned below.

  • Firstly, the time-sharing system provides the advantage of Quick Response
  • Secondly, it avoids duplication of software
  • It reduces CPU idle time

What Does (CTSS) Compatible Time-Sharing System Mean?

Compatible Time-Sharing System allowed multiple users from different areas to access a single computer simultaneously.
Compatible Time-Sharing System, CTSS was demonstrated on MIT’s IBM 709 in 1961 as an experimental time-sharing system. MIT’s one of main projects “Project MAC” is running on a Compatible time-sharing system. The MIT scientist, Fernando Corbató, and two of his colleagues started working on the design of the Compatible Time-Sharing System (CTSS).

According to Wikipedia, “CTSS used a modified IBM 7090 mainframe computer that had two 32,768 (32K) 36-bit-word banks of core memory instead of the normal one. One bank was reserved for the time-sharing supervisory program, the other for user programs.”

CTSS allows users with a set of commands to manipulate files and run different programs through a terminal. This time-sharing system was extremely successful and became ready to use. Although it has some limitations, it was used for time-saving while sharing information through computer systems.

Features of Compatible Time-Sharing System (CTSS)

An experimental time-sharing system became the initial version of the Compatible Time-Sharing System CTSS. CTSS was the first-ever open demonstration of time-sharing. The features of a compatible time-sharing system are as follows.

  • CTSS had one of the first computerized text formatting utilities, called RUNOFF.
  • It had one of the first inter-user messaging implementations, possibly inventing email.
  • CTSS had the text editor QED.
  • CTSS was the first computer system to implement password login.

What is a time-sharing system? Explain with example?

The time-sharing operating system allows the main computer system to be shared by a large number of individuals from different locations. By the use of this operating system, every program, in turn, provides the use of the CPU for a fixed period. At the end of the time, the program will interrupt and the next program resumes execution.

Time-sharing OS provides a specific time to perform a task and every task has its own specific time for performance. Multiple applications on the computer system can run at the same time.
The main objective of this time-sharing system is to increase user and overall computer system productivity.
Some Examples of Time-Sharing Operating System

  • UNIX.
  • Multics.
  • Linux.
  • Windows 2000 server.
  • Windows NT server.
  • TOPS-10 (DEC)
  • TOPS-20 (DEC)

What is the Difference between Multiprogramming and Time-Sharing System?

Multiprogramming allows more than one program and uses a central processing unit (CPU) effectively. It also allows users to use CPU and input-output devices more efficiently.

Time-sharing delivers sharing of data and computing resources between multiple users at once. As this system will allow several users to work on a single computer system simultaneously, it would minimize the cost of providing computing facilities.

The main difference between these two operating systems is that multiprogramming effectively utilizes CPU time by allowing several programs to use the CPU simultaneously. With the time-sharing system computing resources are provided to several users who are looking to use similar resources at the same time.

It also provides each user with a terminal that feels like using the central processing unit alone. Both the operating systems use the same terminology to share the CPU time between several users at once.

Features of Time-Sharing of Operating System

The time-sharing operating system performs multiple tasks at once, hence in simple words, we can also call it a multitasking operating system. It has some important features as mentioned below:

  • Each user grabs dedicated time for all operations.
  • Multiple online users can use the same computer at the same time.
  • End users make feel that they monopolize the computer system.
  • Better interaction between users and computers.
  • The user’s request will make in a small-time response.
  • It does not need longer have to wait for the last task to end to get processor.
  • It can make quick processing with a lot of tasks.

Advantages of Time-Sharing Operating System

In a time-sharing system, every task has explicit time.
The assignment exchanging time is also minimum so applications don’t get waste. Several applications can run simultaneously with time-sharing operating system. It has some following advantages:

  • With a time-sharing operating system, every task makes the same opportunity.
  • It is easy to use and user-friendly time-sharing system
  • It helps to increase the performance of the entire system.
  • Multiple applications can run at once.
  • More efficient and convenient to use
  • It eliminates the replication of software.
  • Interactive computing
  • Decreases paperwork
  • A time-sharing operating system decreases CPU idle time.


In Conclusion, businesses having a lot of tasks to be done can go with the time-sharing operating system. All the tasks can be done on time and no task gets interrupted by the computer system. With this system, each activity and user can get its time for the operation. Time-sharing operating systems give time to apply individual tasks and other applications also so that all system performs correctly.

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