Maintained by Institute of Electrical an Electronic Engineers (IEEE).
Supported by American National Standards Institute (ANSI).
Supported by International Standards Organization (ISO).
Defines rules for standard interfaces between application programs and UNIX-based operating systems.
E.g.:
Definition of a process:
Process id.
Parent process id.
User id.
Group id.
Current working directory.
Process start date/time.
Other things…
Definition of a 'login' (see /etc/passwd):
User login name.
User id.
Group id.
User full name.
Home directory.
Shell.
Etc.
Problem:
Posix is a standard among many (HTTP, HTML, XML, TCP/IP, C, C++, etc.). Think
of some of the advantages and disasvantages of standards in general. Who
controls these standards? Who do they benefit?
Minix.
Linux: born in 1991, developed by Linus Torvalds while at Helsinki University of Technology.
1980s:
Richard Stallman and the Free Software Foundation develop the GNU OS. By
1990 they have all the utilities but lack a kernel.
1992: Linus Torvalds builds a kernel, calls it Linux.
Others distribute the Linux kernel with the GNU utilities and call the whole package Linux.
Richard Stallman insists that it should be called GNU/Linux.
For giggles, Linux users, run >uname -o (OS) and >uname -s (kernel). If the result of >uname -o is GNU/Linux, do a man on uname and check the copyright of the command.
MacOS X.
Others: See Stair & Reynolds, pp. 149-156 & Table 4.3. (careful; the list is iffy again)
Problem: What are some criteria for selecting an OS or switching to another one?
Reliability.
Security.
Legacy.
Hardware platform availability.
Customizability.
Architecture.
Etc.
Trends: Thibodeau (2003) Far From Legacy, but Far More Challenged:
2002: Unix OS expenditures > Windows/Linux combined.
2007: Windows catches up.
Why is Linux welcome:
Allows equipment savings while retaining Unix advantages (e.g., United Parcel Service).
Allows Unix advantages on Intel architectures.
Creates competition ==> forces quality improvements across the board.
Who's afraid and what are they doing?
Sun Microsystems: both Solaris and equipment are threatened ==>
Solaris available on Intel architectures.
Supports Linux on Intel systems.
Open Solaris.
Emphasizes Java.
IBM/HP: HP-UX/AIX and equipment threatened ==>
Porting Linux to HP/IBM equipment.
Scaling Linux to larger, Shared memory Multi Processor (SMP) machines.
64-bit Linux computing.
Software development and consulting services around Linux.
