- Computer System Structure
- OS 所擔任的角色以及目的
- CPU 延遲時間過長原因與解決策略
- Different type of OS
Computer System Structure
主要由4個部分所組成 :
- Hardware : (CPU,Memory,I/O devices)
- Operating System : (RAM,Shared by User)
- Application Programs+System Program
- Users
Note.
“Bare machine” : 純粹只有硬體組成，其上無其他OS及System Program
“Extended machine”: Bare machine+OS(or System Program)或APP
OS ' s Role
- 提供一個讓User 易於操作電腦之溝通介面
- 提供一個讓User Program易於執行之環境
- 作為一個 Resource(資源) 的管理者協調分配 Resource(CPU、Memory 、I/O) ， 期望Resource可被有效利用
- 作為一個監督者，監控所有Process 執行，避免Process 之有意或無意之 破壞，造成 System重大危害
追求『公平』與『效率』，雖然兩者基本上是矛盾的
(e.g： FIFO(公平)與SJF (效率))
CPU 延遲時間過長原因與解決策略
Different Type of OS
Multi-programing
Mechnism vs Policy
Mechnism 和 Policy 必須分開。
Mechanism and policy must be separate to ensure that systems are easy to modify. No two system installations are the same, so each installation may want to tune the operating system to suit its needs. With mechanism and policy separate, the policy may be changed at will while the mechanism stays unchanged. This arrangement provides a more flexible system.
