Operating System

주소 한 개가 가리키는 단위: 1 byte주소 비트 수 → 주소 공간: 비트 수가 N이면 2^N개의 주소 표현전체 메모리 용량: 각 주소가 1바이트씩 할당되므로, 총 2^N byte16 bit → 64KB32 bit → 4GB주소 크기 = 프로그램 크기A program

Running Dynamic Code One basic function of an OS is to execute and manage code dynamically Command line terminal Icon double click Jobs/tasks run as

Are Processes Enough? * Possible scenarios * A server with many clients (e.g. webserber) process: context switching -> overhead A powerful computer

Priority Scheduling SJF, STCF are both priority schedulers Priority = CPU burst time * Problem with priority scheduling * * Starvation*: high priori

simple: 모든 process에게 똑같은 CPU time 나눠주기but, MLFQ는 queue의 종류가 여러가지 We have examined schedulers designed to optimize performance Minimum response times

CPU needs a first instructionMemory needs initial code/dataI/O needs to know how to communicateFirmware는 hw와 sw의 중간 Installed with a computer in non v

Physical vs Virtual Memory Limitation of physical memory 1. Protection and Isolation ruin other process or access kernel memory overwrite 2. Pointers

If a process access a page that has been swapped out, page fault occursA page-fault occurs and the instruction pauses접근하려는 게 DRAM에 없으면 오류 The OS can s

Hard dirives are relatively fast, persistent storageHow to cope with disk failure?Mechanical parts break over timeSector may become silently corrupted

Cheapest way to store large amounts of data Slowest component in most computersFragile mechanical components can breakDisk motor is extremely power hu

Typically 512 or 4096 bytes(=page size -> easy to swap)Individual sector writes are atomicMultiple sectors writes may be interrupted(torn write)Sector