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tags: 作業系統
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# 作業系統 Ch2 Operation system structure

### OS Service
- user interface
- I/O operation
- error detection
- file manipulation
- program execution
- communication
- resoure sharing
- security & protection
- accounting

### UI
- shell - sometimemulti flavor implemented

### system call pass parameter
- register
- stack
- table、block

### system program
- file management
- status info
- file modification
- programming - language support
- program loading and execution
- communication
- background service: run in user context(ex:daemon)
- applicaiton service: don't pertain to system

### implementation
- port: high-level language easy to port to other hardware

### kernal environment structure
- simple | MS-DOS
- application program -> resident system program -> MS-DOS device driver -> ROM BIOS device driver

- more complex | Unix (ex: BSD Unix)
- system program 、 kernel
- layered approach
- abstraction
- microkernal | Mach <-> monolithic
- move service from kernal -> user
- msg passing (overhead)
- module
- loadable kernal module
- hybrid

### Debugging
- core dump: application failure
- crash dump: OS failure
- trace listing
- profiling: periodic sampling of instruction look for statistical trend

### system boot
- firmware ROM hold init boot code
- GRUB: bootstap loader