Linux is a free implementation of Unix developed by Linus Torvald. It supports a wide variety of hardware such as modems, CD-ROM drives, SCSI, sound cards, scanners, etc.. A wide variety of software is available, including Motif (which isn't free, however). Most public-domain Unix/X11 packages will compile out of the box with xmkmf or make. X and X extension libraries are included.
Among the programs included in the Slackware distribution (some pre-compiled, some as kits) are:
Mosaic, TeX, Ghostscript,
xv, flexfax,mpeg-play,sox,emacs, gcc ,gcc++,workman,pine,f2c,cjpeg
Many networking tools are included, and start up out of the box, such as ftp, mail, finger, news,etc. It is easy to install software such as httpd.