Linux and Other Software Projects

In last week's article, I talked about the beginning of Linux. Starting this week, I want to expand on that beginning, talking about pieces of Linux and the Linux movement that have made it what it is today and what it will be in the future. This week's column and program are about what other efforts have contributed to the product we now call Linux.

Last week, I talked about how UNIX and Minix had influenced Linus' initial work. These operating systems set the initial direction, but they were not the only influence. Others include The GNU project of the Free Software Foundation (FSF), UNIX-like code developed at UC Berkeley, and the IEEE's POSIX standard. In addition, the availability of powerful and inexpensive computer hardware certainly helped set the direction.

The FSF's GNU project was started in order to make a free, UNIX-like operating system, complete with a full set of development tools and utility programs. While the operating system itself (the HURD) had never really made it, the related tools have made a significant contribution, first to the UNIX area itself and then to Linux.

For example, GCC, the GNU C Compiler, has been adopted or made available on many computer systems, (including those from Hewlett-Packard and Sun) for years. Emacs, a text editor that some use as their total work environment, has also been made available for all UNIX and many non-UNIX-based computer systems.

UNIX-based systems and their derivatives include hundreds of utility programs. They perform general file management functions, edit and manipulate data files and, in general, offer many capabilities to users of the systems. These programs are licensed products--not something that could be included with a free operating system such as Linux. To turn Linux the operating system into Linux, a complete distribution, GNU utilities were adopted.

Besides the GNU utilities, a large set of utility programs were developed at the University of California at Berkeley. Many of these utilities were initially based on UNIX code from AT&T, but the most recent release of those programs is free of the AT&T code. This made it possible to include these programs with Linux distributions as well. There are many programs, but the most obvious are the Berkeley print spooling system and the sendmail mail transfer agent.

In addition, there are Berkeley-based operating systems. The three flavors are FreeBSD, NetBSD and OpenBSD. Some code and many ideas from the BSD systems have been included in Linux as well.

Back when UNIX was thought to be the one true operating system, the idea of a vendor-independent standard came up. After all, UNIX was a product of AT&T. No matter which UNIX-based computer system you were buying, the licensing went back to AT&T.

The POSIX standard, a product of IEEE, is a set of standards that define how things look--not how they are implemented. For example, there is a standard for the command interpreter or shell. It specifies what the user sees regarding capabilities. Software developers are then free to develop a shell that offers the specified capabilities.

POSIX compliance became important enough that, in addition to all the UNIX vendors, other OS vendors were attempting to make their OS comply. This included Digital's VMS system and Microsoft's NT, with each of these implemented as an add-on.

POSIX compliance has been less than perfect for all vendors, but Linux comes as close as any and much closer than the majority of the vendors. What this means is it is extremely easy to take an application written to run on any UNIX system and re-deploy it on a Linux-based system.

One final thing that has influenced Linux development is the capabilities of new computer hardware. While UNIX was born and developed back in the days of 10-character-per-second teletype terminals, Linux is a recent happening. Therefore, it doesn't have a lot of the baggage UNIX includes.

Also, as the Linux design model is open (anyone can see what the code looks like in a Linux system and can contribute to the development effort), it evolves much more quickly than a closed system. This means that as new technology appears, code can be developed and tested to support the new technology.

The downside is that Microsoft works with hardware developers so they will be aware of the hardware before the Linux market is. However, with people willing to test software on a moment's notice on diverse hardware, the Linux community can quickly debug drivers for new software.