Introduction to UNIX
Intro to OS
What is OS?
- software that sits between hardware and other software
- core part is called the “kernel”
- ex) Windows, Linux, Mac OS
What does OS do?
- a dictator and a servant at the same time
- controls hardware resources and logical resources
- provides a (virtual) environment in which programs run
- linear address space
- exclusive use of CPU
- hardware devices that responds to nice, easy commands
How does OS do that?
- privileged operations (aided by CPU)
- periodic timer interrupts
- predefined entry points into the kernel: system calls
History of UNIX
1945-1970:
- vacuum tubes
- mainframes with punch cards
- IBM 360
- MULTICS
1970: Ken Thompson & Dennis Ritchie invent UNIX and C at Bell Labs
- most of UNIX was written in C rather than in assembly
- inexpensive source code license to universities
- UNIX V6 in 1976, V7 in 1978
Since then, many UNIX variants come and go
- AT&T System V Release 4 (SVR4)
- 4.4BSD (Berkeley Software Distribution)
- and many others: Microsoft Xenix, IBM AIX, HP-UX, IRIX, etc.
Currently, four main competitors remain:
- Linux: created by Linus Torvalds in 1991
- Solaris: SVR4-based commercial offering by Sun
- FreeBSD: based on 4.4BSD
- Mac OS X: combo of Mach kernel and FreeBSD
In the meantime, OS for personal computers evolved in parallel:
- 1977: CP/M by Kildall - dominant OS for 8-bit PCs
- 1977: Apple II by Steve Jobs and Steve Wozniak
- Early 80s: MS-DOS for IBM PC by Microsoft
- 1984: Apple Macintosh
- 1985-1996: NeXT by Steve Jobs
- Late 80s & early 90s: MS Windows up to 3.11
- graphical shell on top of MS-DOS
- Mid 90s to the present: Windows NT, 2000, XP, 7, 8, 10
- true 32/64-bit OS comparable to UNIX
- 2001-present: Mac OS X
Last updated: 2018-01-18