Four features of the operating system
table of Contents
A concurrent
two, sharing
three virtual
four asynchronous
A concurrent
1, Concurrency: refers to multiple events occur within the same time interval. The performance of the macro occur simultaneously, occur alternately micro
2, in parallel: a plurality of events occurring simultaneously at the same time
3, the operating system concurrency: a computer system there are a plurality of simultaneously running programs
4, single-core CPU can only run a program, the operating system will coordinate multiple programs run alternately (micro concurrent, parallel macro)
5, in fact, the operating system is accompanied by a "many-to-program technology" and appeared, so the operating system and programs are concurrent born with
Second, share
1, sharing (sharing of resources): the system resources available memory, while the use of multiple concurrent processes
2, Share Category:
- Sharing mutually exclusive: a period of time only allows a process to access
- While sharing: a period of time to allow multiple programs to simultaneously access
While understanding: concurrent micro, macro parallel
3, examples of life:
- Sharing mutually exclusive: use the printer
- While sharing: access hard disk resources
4, sharing: multiple concurrent processes commonly used system resources
5, the relationship between concurrency and sharing of: QQ micro letter and send a message, you need to access the hard disk resources
- QQ, micro-channel concurrency: no concurrency, memory is only one program running, it will not make sense to share
- Common access hard disk resources: no sharing, QQ, micro-channel can not access resources at the same time, it can not send messages while concurrently also lost to the meaning
- So complicated by the presence of each other and share
Third, virtual
1, the virtual: entity mapping physical really present in a number corresponding to a plurality of logical was not present on the
2, Virtual Directory:
- Virtual memory technology: the use of space division multiplexing
- Virtual processor technology: the use of time division multiplexing technology
- Loss of concurrency, it will be meaningless virtual
Fourth, asynchronous
Asynchronous: In a multi-channel programming environment that allows multiple programs concurrently, but due to limited resources, the implementation process is not always in the end, but stop and go to the progress of the implementation of unpredictable forward
Note: no concurrency and shared, virtual and asynchronous out of the question, as well as concurrency and sharing is the most basic features, and the presence of each other