2.7 I/O System OverviewThe basic model of the UNIX I/O system is a sequence of bytes that can be accessed either randomly or sequentially. There are no access methods and no control blocks in a typical UNIX user process. Different programs expect various levels of structure, but the kernel does not impose structure on I/O. For instance, the convention for text files is lines of ASCII characters ..

Kernel Services The boundary between the kernel- and user-level code is enforced by hardware-protection facilities provided by the underlying hardware. The kernel operates in a separate address space that is inaccessible to user processes. Privileged operations—such as starting I/O and halting the central processing unit (CPU)—are available to only the kernel. Applications request services from ..

ZMQ Request-Reply pattern ‘Hello World’ client/server example Client sends “Hello” to the server Server replies with “World” 1:1 TCP echo 서버와 유사 Synchronous REQ-REP socket 어플리케이션은 동기, 통신에 대한 부분은 알아서 비동기로 처리됨 Client issues send() and then recv(), in a loop 클라이언트가 선택한 패턴 - 리퀘스트 패턴 / 서버는 리플라이 패턴 Doing any other sequence (e.g., sending two messages in a row) will result in a return code of -1 from t..

Bootstrapping in Linux - CPU - smart X -> 매우 빠르게 메모리에서 명령어를 읽고, 실행하는 것 - ROM - Read only memory - 읽기 전용 메모리, 영구적으로 저장하는 비휘발성 메모리 - 전원이 꺼져도 존재 -> 처음 부팅될 때 실행할 모드 + RAM - Random Acess Memery - 휘발성 메모리, 작업 중인 내용을 한시적으로 저장 하드웨어 초기화 및 테스트 - BIOS - Basic input output system - UEFL - Unified Extensible Firmware Interface -> 펌웨어 : 하드웨어에 포함된 소프트웨어 == 롬에 저장된 소프트웨어 -> POST - power on self test 진행 - 메모리 및 i..