What is an Operating System? ? 1. Referee 　　– Manage sharing of resources, Protection, Isolation 　　? Resource allocation, isolation, communication 2. Illusionist 　　– Provide clean, easy to use abstractions of physical resources 　　　　? Infinite memory, dedicated machine 　　　　? Higher level objects: files, users, messages 　　? Masking limitations, virtualization 3. Glue 　　– Common services 　　　　? Storage, Window system, Networking 　　　　? Sharing, Authorization 　　　　?Look and feel

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Four fundamental OS concepts

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1. Thread 　　– Single unique execution context 　　– Program Counter, Registers, Execution Flags, Stack 2. Address Space w/ Translation 　　– Programs execute in an address space that is distinct from the memory space of the physical machine 3. Process 　　– An instance of an executing program is a process consisting of an address space and one or more threads of control 4. Dual Mode operation/Protection 　　– Only the “system” has the ability to access certain resources 　　– The OS and the hardware are protected from user programs and user programs are isolated from one another by controlling the translation from program virtual addresses to machine physical addresses

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ps: difference between threads 與 processes

　　-?process encapsulate one or more threads sharing process resources 　　-?Processes provides memory protection, threads more efficient than processes?

Some other BIG OS Concepts

　　??Interrupt handlers (including syscall and trap)

?　 ???File System

　　　　– Integrates processes, users, cwd, protection

　　? Key Layers: OS Lib, Syscall, Subsystem, Driver
　　　　– User handler on OS descriptors
　　? Process control
　　　　– fork, wait, signal, exec
　　? Communication through sockets
　　? Client-Server Protocol

轉載于:https://www.cnblogs.com/whuyt/p/4864075.html

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