Chapter 1 What is Unix?ObjectivesUnix Brief HistoryUnix Brief History (Cont.)Slide 5Unix ComponentsSlide 7Unix FeaturesSlide 9ReferenceChapter 1 What is Unix?By C. ShingITEC DeptRadford UniversityObjectives•Understand Unix history•Describe Unix components•Understand Unix featuresUnix Brief History•1969 Ken Thompson, Bell Lab–use assembly language–machine dependent•1970 Dennis Ritchie, Bell Lab–more than 90% code in C language–machine independent •1979 Version 7, Release 4 (SVR4)Unix Brief History (Cont.)•Implement different memory management algorithms–AT&T System III 1980, System V 1983: virtual memory, Bourne shellIPC: message, shared memory, semaphores•V.2–IBM AIX–OSF/1•V.3•V.4, 1986: Korn shell•V.4.1, 1990–SUN OS (Solaris), HP/UX–BSD (Berkeley Standard Distribution): socket networking, C shell, vi•4.2–Apollo•4.3, 1990–SUN OS (Solaris), HP/UX•4.4, 1992–FreeBSDUnix Brief History (Cont.)•1991 Linux by Linus Torvalds: reimplementation of minix for PC architecture, Bash shell•1992 POSIX.1(Portable Operating System Interface): IEEE standardize API: system calls (1988) and commands (1992)•2002 POSIX.2: Standard UNIX Specification (or SUS)Unix Components•Kernel: in RAM–System calls–Interrupts•File systems: directory structures (tree)–Directory contains filenames and location of files–Every device is a file•Process management: share –CPU: time slice 1/10 sec, round-robin–RAM: fixed size page–Disk: fixed size block(1024 Bytes)Unix Components•I/O–Character (device)–Block (regular file)–Network (socket)•IPC (inter-process communication)–Signal: processes in same machine–Pipe: processes in same machine–Socket: processes in different machines–Client/serverUnix Features•Open system–Internal software source code are available (free or low cost)•Platform independent–From PC to supercomputer•Multi-users: round-robin between users•Multi-tasking: process (execution of a program) sharing•Virtual memory–Swap space at least 2 times of RAMUnix Features•Simple view of devices-Files (data unit on storage)–Peripheral–Network interface–Disk•Efficient, robust, simple•Lots of Utilities: tools for users to interact UNIX–Command line interpreter: process shell command•System calls similar to library routines–Processes use system-calls to interact with Kernel•Lots of commercial software•GUI: X WindowReference•Unix History: Chapter 16•Unix internal: Chapter