Operating systems using multiprogramming technology have the following characteristics:
① Concurrency. It refers to the occurrence of two or more events or activities within the same time interval. The operating system is a concurrent system, and concurrency is its important feature. The concurrency of the operating system refers to the simultaneous existence of several running programs in the computer system. Therefore, it should have the ability to process and schedule multiple programs to execute simultaneously.
② sharing. Sharing means that resources in a computer system can be shared by multiple concurrently executing user programs and system programs, rather than being exclusively used by one of them. There are two forms of sharing: one is sequential sharing. The second is concurrent sharing.
③ Uncertainty. Uncertainty is also called asynchrony. In an environment where multiple programs are executed concurrently, there is a direct or indirect relationship between programs, and the speed of program advancement will be affected by the operating environment. If it cannot be controlled correctly, the execution results will be different due to different operating environments.
④ Virtuality. Virtuality refers to a management technology in the operating system, which is a technology that turns one physical entity into multiple logical counterparts, or multiple physical entities into one logical counterpart. The so-called virtual refers to the functions that are not provided physically, but are logically available. It appears to the user as if it were a function that was physically present. The purpose of adopting virtual technology is to improve resource utilization and provide users with an easy-to-use, convenient and efficient operating environment.
Multiprogramming technology is to store several mutually independent programs in the main memory of the computer at the same time, and they run interspersed with each other under the control of the operating system.
Features of multiprogramming:
1. Multi-channel: Several independent programs are stored in the main memory of the computer at the same time.
2. Macroscopically parallel: several programs that enter the system at the same time are in the running process, that is, they all start to run, but they have not finished running.
3. Microscopically serial: From a microscopic point of view, multiple programs in the main memory occupy the processor in turn or time-sharing and run alternately.
Multiprogramming technology is to store several mutually independent programs in the main memory of the computer at the same time, and they run interspersed with each other under the control of the operating system.
Features of multiprogramming:
1. Multi-channel: Several independent programs are stored in the main memory of the computer at the same time.
2. Macroscopically parallel: several programs that enter the system at the same time are in the running process, that is, they all start to run, but they have not finished running.
3. Microscopically serial: From a microscopic point of view, multiple programs in the main memory occupy the processor in turn or time-sharing and run alternately.