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Chapter 1 What is Unix?

Chapter 1 What is Unix?. By C. Shing ITEC Dept Radford University. Objectives. Understand Unix history Describe Unix components Understand Unix features. Unix Brief History. 1969 Ken Thompson, Bell Lab use assembly language machine dependent 1970 Dennis Ritchie, Bell Lab

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Chapter 1 What is Unix?

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  1. Chapter 1 What is Unix? By C. Shing ITEC Dept Radford University

  2. Objectives • Understand Unix history • Describe Unix components • Understand Unix features

  3. Unix 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)

  4. Unix Brief History (Cont.) • Implement different memory management algorithms • AT&T System III 1980, System V 1983: virtual memory, Bourne shell IPC: 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 • FreeBSD

  5. Unix 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)

  6. 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)

  7. 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/server

  8. Unix 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 RAM

  9. Unix 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 Window

  10. Reference • Unix History: Chapter 16 • Unix internal: Chapter 14

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