Q. Explain about Time Sharing Systems?

Time Sharing Systems

• Multi-programmed batched systems provide an environment where various system resources (for illustration CPU, memory, peripheral devices) are utilized effectively.

• Time sharing or multitasking is a logical extension of multiprogramming. Multiple jobsare executed by CPU switching between them however the switches takes place so frequently that users may interact with every program while it is running.

• An interactive or hands-on computer system provides on-line communication between user and system. The user gives instructions to operating system or to a program directly and receives an immediate response. Typically a keyboard is used to provide input and a display screen (like a cathode-ray tube (CRT) or monitor) is used to provide output.

• If users are to be able to access both code and data conveniently, an on-line file system should be available. A file is a collection of related information defined by its creator. Batch systems are applicable for executing large jobs which need little interaction.

• Time-sharing systems were created to provide interactive use of a computer system at a reasonable cost. A time-shared operating system employs CPU scheduling and multiprogramming to provide every user with a small part of a time-shared computer. Every user has at least one separate program in memory. A program which is loaded into memory and is executing is usually referred to as a process. When a process executes it characteristically executes for only a short time before it either completes or needs to perform I/O. I/O can be interactive; which is, output is to a display for user and input is from a user keyboard. Because interactive I/O typically runs at people speeds, it can take a long time to complete.

• A time-shared operating system enables many users to share the computer simultaneously. Because every command or action in a time-shared system tends to be short, only a little CPU time is required for each user. As the system switches rapidly from one user to next, every user is given the impression that she has her own computer while actually one computer is being shared among many users.

• Time-sharing operating systems are even more complicated than are multi-programmed operating systems. As in multiprogramming various jobs should be kept simultaneously in memory that requires some form of memory management and protection.